everyone wondered, did her work cost her her life? >> i remember them telling me did she come into a lot of money she couldn't explain? >> maybe she was selling secrets? >> maybe. >> that's like out of a spy novel. >> what about other secrets? the personal kind. >> we knew they were having issues. >> right before they got married she found out that he was cheating. >> but somewhere out there was a stranger keeping secrets too. >> my data guy starts going through her facebook. >> she made reference to firearms in her social media. >> we saw that they were communicating her gas mileage. what a weird thing to do. >> a mystery that would drag on for months. and then, one final secret uncovered by science. >> you start peeling the layers back until the number is visible. hello and welcome to "dateline." texas native karlyn ramirez grew up surrounded by friends and family, then moved east after joining the army. she had a job she loved, a baby daughter she adored and her whole life ahead of her. then she was shot dead in her home. her killer thought he'd covered his tracks. but investigators were determined to follow the clues, exposing a plot so devious it defied imagination. here's andrea canning with "the alibi." >> mommy. >> reporter: across the spectrum of love is there any more precious than that of a mother for her daughter? ♪ you are my sunshine ♪ ♪ my only sunshine ♪ our story is about that maternal tie that endures from generation to generation. it begins in a military town near the mexican border. del rio, texas. a small city anchored by the laughlin air force base. karlyn ramirez grew up there. she was an easygoing child says her mom, susan garcia ramirez. >> karlyn, when she was young, she was real calm and quiet. karlyn loved to sing. she would sing all the time. ♪♪ whenever she was out with her friends, you know, she would sing for them. >> reporter: rosanna flores was one of those friends. what was it about karlyn you that wanted to be her friend? >> her smile. her voice. her big heart. i can honestly say she never saw any bad in anyone. >> her friends, anais avara and valerie mckechny, say it wasn't all about singing. scl we'd go to the local bar here and we'd dance. ♪♪ >> and they say the dancing could literally happen anywhere. that's karlyn in black. >> fun times at the walmart parking lot. >> only in a small city, right? >> she went to college in del rio, started in nursing and then transferred to criminal justice. nothing that prepared her mom for what she did at 22. enlist in the army. >> she didn't ask me, she didn't get my opinion, she told me after she had done it. >> your family is a military family? >> we are. my dad was air force. my sister is retired air force. and then i was in the army reserves. >> after specialty training in information technology the army sent karlyn to south korea. off duty she found time to give back. >> she found herself volunteering at an orphanage. well, she starts sending me pictures of a little boy that she's in love with, and she says mom, i want to adopt him. i said, no. >> in korea karlyn found another kind of love. she began dating a handsome sergeant named maliek kearney. >> she was attracted to his confidence, to his air, the way he carried himself. >> he was a decorated soldier. >> yes. >> did she like that about him? >> yes. they worked out together and they ran. they were very competitive. >> karlyn gushed about maliek to her friends. >> she said that he was a great man, that he treated her right. and then she told me they were engaged. >> engaged and expecting. pregnant, the army drafrd her to fort meade, maryland, home of the national security agency and one of the agency's most secret and secure facilities. >> was she happy? was she excited? >> she was excited. she started working and absolutely loved it. >> top secret, some of it? >> she would say mom, i can't share anything about what i do. >> meantime, the army moved maliek to fort jackson, south carolina where he trained recruits in chemical warfare. the couple was 500 miles apart. while living by herself in maryland, karlyn became friends with another soldier, marisa manthey. marisa loved working with karlyn. >> she was the light of the office. she was loving. everyone loved her. >> marisa was a single mom with a young daughter. so when karlyn was nearing the end of her pregnancy, they decided to share a house together. >> had a back yard. it had a decent-size kitchen. and it was right by base. >> did you ever have security concerns? about the townhouse or the area. >> we did have. karlyn had mentioned that she came home one day and felt like stuff was moved around in the house. >> really? >> yeah. >> if somebody says that to me i'm getting worried. >> the two women kept the doors and windows locked and worked together to make their townhouse a home. marisa helped karlyn set up a nursery, and then on april 23rd, 2015 catalea vail ramirez was born. grandma susan was on the first flight from texas. >> what was it like seeing karlyn and her new daughter vail together? your baby's had a baby. >> yes, it was amazing. i got her and i wouldn't share her with anyone. >> vail was healthy and beautiful. karlyn radiant. their townhouse was filled with the joyful sounds of karlyn singing to vail. she particularly loved "you are my sunshine." ♪ you'll never know dear how much i love you ♪ >> she was happy. it looked like she found her purpose in life. >> three months after vail was born karlyn and maliek married in a small ceremony in south carolina. after the party karlyn went back home to fort meade in maryland with the baby. >> she said it was hard, the distance and not seeing him all the time. >> susan stayed in touch with her daughter. >> i spoke with karlyn every day, sometimes twice a day. >> but tuesday august 25th would be different. susan called karlyn that morning. >> and she didn't answer. >> and is that -- i mean -- >> that's unusual. >> you have such a close relationship. >> so i waited and i called her again. and she didn't answer. so i sent her an e-mail to her work e-mail. never got a response to that. called her on my lunch break. and she didn't answer. i said, if you do not call me back or message me, i'm going to call the police. >> a now frantic susan reached karlyn's commanding officer at his home. he promised to have someone on the base find her. >> i hang up with him. and i put the phone down. and i hear a ruffle -- in the front rock we have river rock. so i looked out and i saw three uniformed soldiers. >> oh, gosh. >> and i knew. >> that just made me -- >> yeah. sick. that's what it did to me too. >> it's what any relative of a -- somebody in the military dreads. i mean, i'm a marine corps wife myself and it's -- >> it's the last thing -- you don't ever want to have to see that. i yelled my husband's name and i just -- i dropped to my knees, and i said something happened to karlyn. and then they knocked. >> she was right. something had happened to karlyn. and now this mother was about to hear the words every military family dreads. coming up -- >> what'd they say? >> we regret to inform you. just like they always say. >> what the soldiers said next would leave this mom horrified and confused. >> so what scenarios are running through your mind? >> i couldn't even imagine what could have possibly happened. >> when "dateline" continues. ons s you've got the looks♪ ♪let's make lots of money♪ ♪you've got the brawn♪ ♪i've got the brains♪ ♪let's make lots of♪ ♪uh uh uh♪ ♪oohhh there's a lot of opportunities♪ with allstate, drivers who switched saved over $700. saving is easy when you're in good hands. allstate click or call to switch today. your mission: stand up to moderate to severe rheumatoid arthritis. and take. it. on... ...with rinvoq. rinvoq a once-daily pill can dramatically improve symptoms... rinvoq helps tame pain, stiffness, swelling. and for some rinvoq can even significantly reduce ra fatigue. that's rinvoq relief. with ra, your overactive immune system attacks your joints. rinvoq regulates it to help stop the attack. rinvoq can lower your ability to fight infections, including tuberculosis. serious infections and blood clots, sometimes fatal, have occurred... ...as have certain cancers, including lymphoma, and tears in the stomach or intestines, and changes in lab results. your doctor should monitor your bloodwork. tell your doctor about any infections...and if you are or may become pregnant while taking rinvoq. take on ra. talk to your rheumatologist about rinvoq relief. rinvoq. make it your mission. if you can't afford your medicine, abbvie may be able to help. you're clearly someone who takes care of yourself. so why wait to screen for colon cancer? because when caught in early stages, it's more treatable. i'm cologuard. i'm noninvasive and detect altered dna in your stool to find 92% of colon cancers even in early stages. tell me more. it's for people 45 plus at average risk for colon cancer, not high risk. false positive and negative results may occur. ask your prescriber or an online prescriber if cologuard is right for you. i'll do it. good plan. in del rio, texas susan ramirez's husband opened their door to an army casualty notification team. and the worst news imaginable. their karlyn was dead. >> what did they say? >> we regret to inform you. just like they always say. same words. they had a chaplain with them. and couldn't give me any specifics. i asked for the baby. they said that she was in the hospital. >> so what scenarios are running through your mind? >> i couldn't even imagine what could have possibly happened. >> the answers would come 1,700 miles away at karlyn's town house in maryland. homicide detectives kelly harding and dan meyers of the anne arundel county police department were on the case. >> a maintenance person saw a dog walking around into an open back door of the townhome. he called 911. and the officers got there. and karlyn ramirez had been murdered. >> patrol officers led the detectives to a second-floor bedroom and an appalling scene. it was karlyn and her four-month-old daughter together. >> she was laying in the master bedroom, and a little girl was they thought initially also had been murdered. but it turns out that she was just sleeping alongside her mom. the baby was unharmed. >> the investigators began their search for clues with karlyn's body. >> she was laying on the floor near the crib. her pants and her underwear had been removed. >> did that suggest to you that there may have been a sexual assault? >> it's something that you have to consider. >> the crime scene investigation ramped up. csis dusted for fingerprints and collected hair and dna samples. karlyn had been shot three times. ballistics experts traced the bullets' trajectories and recovered a bullet if the floor. they were able to narrow down the weapon to a few different models. >> caliber of the projectile was .357, .38 special. >> of course a hard look at the spouse as homicide investigation 101. so the day after they found karlyn's body detectives flew to south carolina to talk with maliek. >> he'd been placed in an interview room and he was waiting for us. >> they started by asking about karlyn. >> what can you tell us about her? >> she was the love of my life. >> maliek's superior officer had given him only the vaguest of details about what happened to karlyn. >> did he tell you how she passed away? >> i don't know what happened. i miss her. >> the way she was murdered. >> why? >> that's what we're hoping you can help us with. >> i don't know. i don't know anybody that didn't like her or had anything against her. >> they wanted to know maliek's whereabouts the day of the murder. he told them he worked his usual shift monday, leaving around 2:00 p.m. he said he stayed in his apartment until he reported for duty tuesday morning. >> didn't go out monday night, talk to anybody? >> no. i mean, i'll stay at home, text on my phone, something like that. >> the questions got personal. detectives had been told karlyn was planning to divorce maliek. >> i'm telling you as an outsider it looks like y'all were done. she was done with you, right? >> she'd moved on. >> i don't know. >> they learned about a brief relationship karlyn had with another soldier at fort meade shortly before she married maliek. and asked him how he felt about that. >> it was before we were married. and i forgave her. >> did you ever cheat on her when you were in an exclusive relationship with her? >> cheat? no. >> the detectives cut to the chase. >> you didn't kill her, right? >> no. >> did you have someone else kill her? >> no. >> was he being really cooperative with you? >> he appeared to have nothing to hide. >> maliek let them download his phone. and that wasn't all. he volunteered his bank records, offered fingerprints, and provided a dna sample. he gave police permission to search his apartment and car. the detectives got to work. >> right away. we talked to neighbors in his apartment building. they said that his car never left. >> maliek kearney's apartment and car, a distinctive jaguar xjl, came up clean. and all his electronics, his cell phone, and netflix account put him at home that night. 500 miles from the crime scene. police checked toll plazas and license plate readers between south carolina and maryland. there was no sign of maliek's jaguar anywhere on what would have been a 15-hour round-trip. >> would you say that he had a good alibi? >> yes. >> maliek kearney was free to go. the maryland detectives were back to square one. at the beginning of what would become an incredibly complex homicide case. an investigation that would span a half dozen states, involve hundreds of witnesses, multiple government agencies, and a mountain of forensic evidence. >> coming up -- could karlyn's top secret work have cost her her life? >> i wondered if she was targeted or knew something she wasn't supposed to know. >> i remember specifically them telling me, did she come into a lot of money that she couldn't explain? >> when "dateline" continues. "ds most reliable network. we designed our 5g to make the things you do every day, better. with 5g nationwide, millions of people can now work, listen, and stream in verizon 5g quality. and in parts of many cities where people can use massive capacity, we have ultra wideband. the fastest 5g in the world. this is the 5g that's built for you. this is 5g built right. only from verizon. a little more than a week after she was killed private first class karlyn ramirez was buried with full military honors. flags were presented to her parents, husband and daughter. susan had little time to mourn. she was busy caring for karlyn's daughter vale in texas while her father, maliek, was on active duty in south carolina. susan was also doing everything she could to help solve the case. investigators asked again and again, who would want karlyn dead? >> i would say you know, i am racking my brain and i wish i could tell you but i just cannot think of anyone. >> detectives cast a wide net. they spoke with karlyn's roommate marisa multiple times. they were curious about the soldier karlyn had the brief relationship with before she married maliek. could her death have been the result of a love triangle gone bad? >> their line of questioning made me think that they were looking at the soldier that she was involved with. >> the guy she was having the fling with at work? >> yes. >> what kind of questions did they ask about him? >> what their relationship was like. did he love her? did she love him? did maliek know? >> did you have to check into the soldier that she had the little side thing with? >> certainly. and he was devastated that this happened. he provided his phone, his whereabouts. we concluded that he was telling the truth. where he was during the time. >> with the boyfriend cleared, some of karlyn's friends and family thought the murder might be connected to her top secret work at fort meade. >> i wondered if she was targeted or knew something she wasn't supposed to know. because of her job. >> the detectives were looking for any sign that karlyn might have been recruited as a spy by foreign agents. >> i remember specifically them telling me, did she come into a lot of money that she couldn't explain to you? no, she didn't. >> maybe she was selling secrets? that's out of some kind of spy novel. that theory. >> what did you learn about karlyn ramirez's role in the military? >> she was not ajs specialist. >> did you have to explore the fact that maybe this had something to do with her job? >> there was no evidence of a handler or any sort of misbehaving with her information. >> espionage was ruled out. weeks went by without a break in the case. >> homicide detectives are still conducting several interviews. we're still processing evidence from the scene. >> the crime scene investigation intensified. >> they had my house taped off for almost a month, just going through evidence, going through the house, trying to find things, trying to find leads. >> and marisa lived in fear. remembering karlyn's concerns about someone creeping around their townhouse. >> karlyn had said she thought maybe someone had moved things around. did your mind go at all to the possibility that it could have been someone random? >> it even almost seemed like a hit man had did it because it was so meticulously planned out. >> karlyn's roommate told us that they had security concerns, that someone had maybe been in the townhouse at some point. >> it was always something we kept in the back of our minds. >> did you have to consider the possibility that maybe karlyn had a stalker, someone who was watching them, watching her? >> yeah. we looked extensively into her background and into her communication. >> investigators pursued the few leads they had. all the while susan was pushing them for answers. >> two or three times a week. you know. they would hear from me. >> it must have been getting frustrating that she was murdered, her killer's out there. >> yes. >> and her daughter is with you. you must have felt that fear. >> constant fear. vale was not out of our sight. >> but she heard nothing. in april on what would have been karlyn's 25th birthday the family took vale to visit her grave. >> mommy. >> by that time maliek was living nearby. the army had allowed him to transfer from south carolina to fort sam houston. >> he had gotten orders to get closer to the baby. and as close as he could get was san antonio so he could come and spend time with the baby on the weekends. >> the ramirez family struggled to find normalcy. back in maryland the investigation seemed to have stalled. anne arundel county offered a $20,000 reward for information about the case. the reward generated no promising leads. and homicide detectives wondered if karlyn's death could be part of a larger, even more sinister crime. >> detectives turned to the fbi as a stunning new theory takes center stage. coming up -- >> there's no likely suspects. so the first thought is serial killer or some unknown individual. >> and then an eyebrow-raising revelation about karlyn's estranged husband. >> she said that they'd been intimate for several years. >> when "dateline" continues. els , not actors, who've got their eczema under control. with less eczema, you can show more skin. so roll up those sleeves. and help heal your skin from within with dupixent. dupixent is the first treatment of its kind that continuously treats moderate-to-severe eczema, or atopic dermatitis, even between flare ups. dupixent is a biologic, and not a cream or steroid. many people taking dupixent saw clear or almost clear skin, and, had significantly less itch. don't use if you're allergic to dupixent. serious allergic reactions can occur, including anaphylaxis, which is severe. tell your doctor about new or worsening eye problems, such as eye pain or vision changes, or a parasitic infection. if you take asthma medicines, don't change or stop them without talking to your doctor. so help heal your skin from within, and talk to your eczema specialist about dupixent. if your financial situation has changed, we may be able to help. why choose proven quality sleep from sleep number? if your financial situation has changed, because a good night's rest is where muscles recover, and our minds are restored. introducing the new sleep number 360 smart bed. the only bed that effortlessly adjusts to both of you. proven quality sleep, is life-changing sleep. i'm dara brown. here's what's happening. donald trump's mar-a-lago is partially closed after several staff members tested positive for covid. the former president moved to his palm beach club after losing the 2020 election in january. back in new york trump's former personal lawyer michael cohen says that he's had his eighth meeting with the manhattan district attorney's office. the d.a.'s conducting a wide-ranging criminal probe into the former president, his organization and associates. now back to "dateline." welcome back to "dateline." i'm natalie morales. who killed karlyn ramirez? police had cleared karlyn's ex-boyfriend, and phone records showed her estranged husband maliek kearney was hundreds of miles away when she was shot. it was time to broaden the search for answers. soon investigators would make a remarkable discovery buried in a trail of electronic clues. once again, here's andrea canning with "the alibi." >> it had been months since karlyn ramirez had been found murdered at home with her infant daughter in her arms. with all leads exhausted, homicide detectives wondered if karlyn's death might be part of a pattern. they reached out to profilers with the fbi's behavioral analysis unit. fbi special agent jonathan schafer would join the team. >> the story that the husband's in south carolina, there's no apparent likely suspects. so the first thought is serial killer or some unknown individual. that's where they'd requested the profiler. >> had there been any serial killers in the area that could possibly tie to this then? >> no. there wasn't at that time. it was a long shot. >> did this lead anywhere, contacting the b.a.u.? >> their opinion was that probably somebody close to her did this. >> with no obvious progress in karlyn's case, friends began to despire. >> it scared me that karlyn was never going to get her justice. >> but what they didn't know was maryland detectives and the army's criminal investigation division had been quietly collecting a massive amount of electronic information. of course police had initially talked to karlyn's estranged husband, maliek. but his phone records had indicated he was at home. 500 miles away from karlyn was murdered. but months after they'd asked for it police finally had not only maliek's data but the data of everyone who had been contacted from his phone. >> we then requested and received information from the people that maliek was communicating with. >> all their tedious digital searching paid off. it was a development that took them in a whole new direction. buried in maliek's phone records were numerous calls and texts with a woman named dolores delgado. a former soldier living in florida. when investigators pored over her phone records, a dramatic discovery. >> we had learned that dolores was actually in south carolina during the time of the murder. >> that phone data not only had dolores in south carolina, it placed her in maliek's apartment complex. >> this must have been a big break. >> this was a huge break. >> on a wednesday afternoon in march 2016 detective harding turned up unannounced on dolores's doorstep in coco beach, florida. >> knock on the door and i say hi. i'm detective harding. i'm from anne arundel county, maryland. i'd like to talk to you. >> that's a shock. >> and she was very shocked. she said, about what? maliek? and i said yes, actually. >> in an interview room at the sheriff's office the detective asked dolores about the night of the murder. if she was in maliek's apartment and if he was with her. >> she admits that she was there that night. >> what happened at maliek kearney's house? >> she was in the living room and he went to bed. as far as she knew, he was there the whole time. >> was this a sexual relationship? >> she said that they had been intimate for several years. >> so she's a long-time pairamore. >> they definitely had a long relationship. >> detectives now knew one thing for sure after talking to dolores delgado. maliek kearney had lied to them. about being faithful to karlyn for starters. >> but more critically about what happened the night of karlyn's murder. >> stay at home, text on my phone. >> if you have somebody that can account for your whereabouts during the time of the murder, why wouldn't you offer that to us? why would you keep that secret? >> the detectives had to consider that maybe maliek just didn't want to admit he was cheating on his wife with dolores. they took a closer look at this girlfriend, who told them she and maliek hooked up when they were both serving in kuwait years earlier. then, when harding and meyers examined dolores's phone data, they learned she also lied. about owning a gun. >> she told me that she was almost ignorant about firearms. but in her phone i could see that she was looking for a very particular firearm. >> on her phone there was a text that read "my last .357 i paid 400. so i want to stay in that range." detective meyers dove deeper into dolores's life. >> my data guy here starts going through her facebook. >> there were some things going on with firearms, some information about where she purchased firearms previously -- >> this is the woman who had no knowledge of firearms. >> right. >> the posts led meyers here. to a gun shop near dolores's home. the shop had a sales receipt and a federal firearms transaction record for a taurus .357 revolver. both forms were made out to dolores delgado. the revolver dolores bought matched the caliber of gun that had killed karlyn. >> we saw that this gun was one of the ones on the list. >> of itself this purchase of a gun wasn't a smoking gun. but the detectives had to wonder why dolores would lie to them about owning a weapon. and there was something else. meyers soon learned that dolores had put a box of .38-caliber ammunition up for sale on facebook. >> now, that's obviously you can't say it's the same bullets, but it matched all the characteristics. >> all this sleuthing took months. and while the detectives were working, dolores moved to san antonio, texas, into an apartment not far from maliek kearney. 150 miles west. karlyn's mom knew nothing about this new person of interest despite staying on the detectives. >> it's me again. i just don't want you to forget my daughter because she was very much loved. >> the investigation now encompassed a half dozen states. but maryland detectives and fbi agents were homing in on dolores delgado. >> what were you all learning about the relationship between maliek kearney and dolores delgado? >> just how, for lack of a better term, weird it was. they were friends. they were friends with benefits. they were lovers but not really romantically involved. they were just sort of best friends with romantic bent. >> there was another weird thing. dolores delgado's phone was full of texts between her and maliek kearney that weren't on his phone. and what a twisted story those texts would tell. >> coming up -- a tip from a complete stranger could blow the case open. >> he said one night we got rid of a gun. i think that was your murder weapon. >> i mean, do you get calls like this every day? this is pretty remarkable. >> i wish. but we don't. >> when "dateline" continues. n s ♪ for the maestros of the creamiest-ever, ♪ ♪ must-have smoothies. ♪ ♪ it's irresistibly delicious.♪ ♪ more almond breeze, please! ♪ you could take your ulcerative colitis treatment in a different direction. talk to your doctor about xeljanz, a pill, not an injection or infusion, for adults with moderate to severe ulcerative colitis when a certain medicine did not help enough. xeljanz is the first and only fda-approved pill for moderate to severe uc. it can reduce symptoms in as early as two weeks, improve the appearance of the intestinal lining, and provide lasting steroid-free remission. xeljanz can lower your ability to fight infections. before and during treatment, your doctor should check for infections, like tb and do blood tests. tell your doctor if you've had hepatitis b or c, have flu-like symptoms, or are prone to infections. serious, sometimes fatal infections, cancers including lymphoma, and blood clots have happened. taking a higher than recommended dose of xeljanz for ra may increase risk of death. tears in the stomach or intestines and serious allergic reactions have happened. you could take your uc treatment in a different direction. ask your gastroenterologist about xeljanz. is skincare from around the world better than olay? to find out, olay faced the world. we tested our vitamin b3 formula and beat japan's top moisturizers. south korea's most innovative. and even the $400 french cream. olay regenerist faced 131 premium products in 12 countries, over 10 years. olay's hydration was unbeaten every time. olay. face anything. it was a bittersweet day in august 2016 when karlyn ramirez's loved ones celebrated her life. on the first anniversary of her murder. back east lead detectives kelly harding and dan meyers had developed two prime suspects -- karlyn's husband, maliek kearney, and his long-time mistress dolores delgado. as they studied the couple's text messages the detectives found something curious. maliek had wiped a lot of texts off his phone that still existed on dolores's phone. her texts made them look at the night of karlyn's death in a whole new light. >> we saw that they were communicating her gas mileage. what a weird thing to do. >> not only that, they were talking gas cans as well. the detectives had dolores's bank records, which showed a purchase at this florida home depot. >> we were able to get a copy of the receipt of her purchase, which included two gas cans. >> finally, they saw the pieces of their puzzle coming together. at the start of the case harding and meyers thought it was unlikely that maliek would have been able to travel all the way to maryland, kill karlyn, and return undetected. but this new evidence changed everything. >> take us through what you believe happened that night. >> dolores is providing all of the tools, the firearm, the ammunition, a vehicle, and really the important alibi of her staying and using his phone. >> the detectives saw it as an elaborate plot. dolores was in maliek's apartment pretending to be him. texting on his phone and streaming his netflix account. creating an electronic alibi while he killed karlyn. this scenario explained why they didn't find maliek's jaguar on any license plate readers. if he did that long drive in dolores's car and carried extra fuel to avoid gas station security cameras, there wouldn't be any trace of him. so he drives straight there. you believe he kills karlyn ramirez relatively quickly? >> at the most he would have been there for ten minutes. >> and then turns around and -- >> and goes back and only stops the one time. just on the roadside in a dark area. to fill up the car. and then immediately gets back in the car and continues to drive. >> just to plan this out so meticulously. did you think about that, just how cold-blooded this was? >> he had a lot of time along the way to say never mind. you know what? what am i doing? this is crazy. driving eight hours by yourself with your own thoughts in the car, you have a lot of time to change your mind. he was determined. >> 13 months after karlyn's death maliek kearney and dolores delgado were arrested in san antonio. >> out of the blue i get a phone call at work. and they ask me if i can come to san antonio that evening. and i said for what? they said there's been an arrest in your daughter's case. but they didn't tell me who. >> susan and her husband made the long drive across west texas. >> that's when i first met the federal prosecutor. they're the ones that told me that maliek had been arrested and his girlfriend. >> what were you learning about dolores? >> i didn't know anything about her. she was no one. she was no one to me. >> assistant u.s. attorneys jim warwick and ken clark met with dolores and maliek. >> i introduced myself to mr. kearney. >> and you also got a chance to speak with miss delgado. >> we presented to her the facts that we had and the evidence that we had compiled against her at that point in time. >> after the arrests came a new lead. a tip to detective harding from an ex-boyfriend of dolores's in florida. >> he called me and said hey, one night i was hanging out with dolores and we got rid of a gun. and he said, "i think that was your murder weapon." >> i mean, do you get calls like that every day? this is pretty remarkable. >> i wish. but we don't. >> investigators met with a tipster in merritt island, florida. he said that not long after karlyn's murder he and dolores delgado had burned some clothing and sneakers here. and that wasn't all. he told them he destroyed a revolver for her, dismantled it, and that the two of them threw the pieces of the gun off this pier. an fbi dive team out of miami was soon on the scene. the water was gin clear that day, and divers found forensic sunken treasure. there on the bottom, rusted, covered with seaweed and entrusted with barnacles, were the pieces of a handgun. the parts were rushed to the fbi crime lab in quantico, virginia. "dateline" was given rare access to the fbi's world-renowned crime lab. in his first ever interview firearms expert brett mills told us how he examined and reconstructed the weapon. first, he carefully cleaned the frame of the gun. >> when i finished cleaning it, there was no serial number there. from our reference collection i knew where the serial number should be. >> it was gone because delgado's ex-boyfriend had ground it away, totally obliterated it. or so he thought. mills had a plan. >> we call it serial number restoration. there are still compressed layers underneath that still has that impression of the serial number. using acid, we can restore that number. >> he demonstrated the process on a gun from the fbi collection. >> once you've polished it, you go in and you literally start peeling the layers back with the acid until the number actually is visible. >> it's amazing how it just reappears, the serial number. >> sometimes it does. other times you might not be able to restore any type of number at all. >> there was another way to determine if they had found the murder weapon. mills would try to match the telltale markings on the bullets that killed karlin to the gun from the river. >> these fine striations that you see are the equivalent of a human fingerprint. >> but there was no way the recovered weapon would ever fire again. so mills removed its barrel, gently cleaned it, and attached it to a working revolver for a test firing. he demonstrated that process with a similar revolver. mills was able to do sex test firings with the recovered gun. everything he found was added to the evidence. now prosecutors would have to see if it would hold up when the defense pointed the finger at someone else in baltimore federal court. >> coming up -- the trial begins. could a major twist tip the case? >> it was right before christmas. >> so it was like an early christmas present? >> yes. >> and then the verdict. and the emotional fallout. when "dateline" continues. -yes, please. [ chuckles ] don't get me wrong, i love my rv, but insuring it is such a hassle. same with my boat. the insurance bills are through the roof. -[ sighs ] -be cool. i wish i could group my insurance stuff. -[ coughs ] bundle. -the house, the car, the rv. like a cluster. an insurance cluster. -woosah. -[ chuckles ] -i doubt that exists. -it's a bundle! it's a bundle, and it saves you money! hi. i'm flo from progressive, and i couldn't help but overhear... super fun beach day, everybody. your mission: stand up to moderate to severe rheumatoid arthritis. and take. it. on... ...with rinvoq. rinvoq a once-daily pill can dramatically improve symptoms... rinvoq helps tame pain, stiffness, swelling. and for some rinvoq can even significantly reduce ra fatigue. that's rinvoq relief. with ra, your overactive immune system attacks your joints. rinvoq regulates it to help stop the attack. rinvoq can lower your ability to fight infections, including tuberculosis. serious infections and blood clots, sometimes fatal, have occurred... ...as have certain cancers, including lymphoma, and tears in the stomach or intestines, and changes in lab results. your doctor should monitor your bloodwork. tell your doctor about any infections...and if you are or may become pregnant while taking rinvoq. take on ra. talk to your rheumatologist about rinvoq relief. rinvoq. make it your mission. if you can't afford your medicine, abbvie may be able to help. if you can't afford your medicine, i'm a verizon engineer, part of the team that built 5g right. the only one from america's most reliable network. we designed our 5g to make the things you do every day, better. with 5g nationwide, millions of people can now work, listen, and stream in verizon 5g quality. and in parts of many cities where people can use massive capacity, we have ultra wideband. the fastest 5g in the world. this is the 5g that's built for you. this is 5g built right. only from verizon. welcome back. maliek kearney was charged in the shooting death of his wife, karlyn. authorities were convinced he and his girlfriend, dolores delgado, devised an elaborate cover-up scheme. investigators recovered a trove of incriminating phone records, and what they suspected was the murder weapon. now the case was headed to court, where a surprise witness was about to take the stand. here's andrea canning with the conclusion of "the alibi." >> in august of 2018 maliek kearney's trial began in federal court in baltimore. he was charged with interstate travel for the purpose of domestic violence resulting in death. the trial would be the culmination of a three-year investigation that had gathered thousands of pieces of electronic and physical evidence in an extraordinary forensic effort. prosecutors jim warwick and ken clark wanted jurors to see maliek kearney not as a superstar army sergeant but as a killer, a soulless executioner who took karlyn's life because she wanted to divorce him and endangered his baby daughter by leaving her in her dead mother's arms. >> he was used to getting what he wanted. relationships could end with maliek kearney, but they had to end on his terms. >> the government showed jurors their digital evidence. >> there was a tremendous amount of electronic data including text messages and photo messages that she shared with mr. kearney. >> including photos dolores had sent maliek of her car's odometer to demonstrate its driving range. and critical correspondence about what they said was the murder weapon. >> one particular text message was very important. he's test-firing the gun, and he texts her saying, "this gun is so darn loud." >> this was part of the prosecutors' plan to put dolores's gun in maliek's hands. fbi firearms expert brett mills told jurors about the results of that serial number restoration test he did on the gun recovered from the river. >> i wound up pulling up all but one of the digits. it wound up matching the bill of sale for ms. delgado's purchase of the revolver. >> is that like a bingo moment for you, when you put this stuff to the test and it works? >> finding out that the number i restored was basically the exact same one that was on her bill of laden, that was awesome. >> and mills had something else to tell the jury. remember, he'd done a test firing like this one through the barrel of the recovered gun. >> and what happened when you testified those bullets and compared them to the bullets from the crime scene? >> when we did a comparison from the victim and we identified those three bullets as having been fired from that revolver that was recovered from the creek. >> the prosecutors introduced that interrogation video of maliek kearney. >> i love this woman. i loved her. i love her to death. >> we did that so that the jury would realize that he was being untruthful. >> do you have a girlfriend now? >> no. >> no? okay. >> and there was something on the tape that prosecutors wanted to be sure jurors noticed. >> incredibly, stupidly, he never actually asks how did my wife die? >> don't you want to know what happened to her? >> they told me that you guys were going to tell me. >> but the u.s. attorneys knew their case would hinge on whether jurors believed their star witness, dolores delgado. dolores had agreed to cooperate three months after her arrest. >> it was right before christmas too. >> it was like an early christmas present? >> early christmas present for 2016, yes. >> prosecutors argued that maliek's long-time mistress would do anything for him. on the stand she backed that up. dolores testified about how she gave maliek her gun, her car, those gas cans, even packed him a sandwich for the drive. and provided him with that crucial electronic alibi. >> in your direct of dolores delgado you said maliek wasn't home that night, was he? and she answered no. was that the beginning of the end for his alibi? >> it is. placing him at a location other thanes where his phone was was critical for this case. >> the prosecution rested. the defense argued the government had proven nothing. they argued someone else did it, that maybe jurors should take a closer look at the government's star witness, dolores delgado. after all, it was her gun disposed of by her ex-boyfriend that killed karlyn. and with karlyn out of the way she'd have maliek all to herself. maliek's lawyers showed the jury a text from dolores to a friend sent before karlyn's murder. "crazy bitch is going to be put out." but the jurors didn't buy it. they quickly found maliek kearney guilty. karlyn's mother had been in court every day. how did that feel? >> yes. >> hearing -- >> he was so glad because with the guilty verdict i don't have to worry that i'm going to have to have any dealings with him. >> at his sentencing the judge called maliek kearney a predator and sentenced him to life plus another ten years on top of that. dolores delgado was sentenced to 17 years for her part in the crime. why do you think maliek kearney and dolores delgado did this? >> i think maliek kearney killed karlyn because she was the first woman in his life that was willing and able to stand up to him and he couldn't handle that. as far as dolores, she was a pawn to kearney, that she would just kind of do whatever he said. >> it was important to karlyn ramirez. it was important to the baby. it was important to the ramirez family to bring them some measure of justice. >> cat trial behind them, the ramirez family and karlyn's friends focused on raising vale and teaching her about her mother. ♪ you are my sunshine ♪ ♪ my only sunshine ♪ >> she sang to her when she bathed her. she sang to her when she dressed her. ♪ my only sunshine ♪ >> vale could still hear that loving voice. karlyn's sister put a recording of her singing inside a teddy bear. ♪ you'll never know dear ♪ ♪ how much i love you ♪ >> we are at this point the constant in her life. we want her to feel protected, loved, everything that i know her mom would have given her. >> that's all for this edition of "dateline." i'm natalie morales. thank you for watching. >> and in the "dateline. i stood there in that hallway where that pool of blood was, where his office was. whoever did this knew this facility and knew it well. >> a head-turning new twist in the crime that stumped everyone from the start >> seven years, we're seeking justice for michelle for almost seven years. >> the mom of tw >> a lot of blood, a lot of trauma. >> there were pry marks on her office door. >> what was ine that office th anybody would want? >> that's the mystery. >> a case blown apart with a secret relationship is revealed. >> i don't get a chance to explain it -- >> you're not controlling this anymore. >>in exposing