friends and family. >> he brought up his association with a motorcycle gang. he came off as kind of a tough guy. >> we'd fool around a little bit, like teasing, sibling teasing i guess you could call it. >> he threatened to take out my whole entire family to get custody of our kids. >> wow. >> a chilling story of danger and duplicity. >> we were trying to figure out who did this. >> he knew the whole time. >> this is the ultimate betrayal. >> reporter: it was 9:00 in the morning on the 25th of june 2015. omaha, nebraska. missy nelson's morning ritual was interrupted by a phone call. it was the bank where her daughter jessyka worked. she was an hour late. >> i was like, "what? what do you mean she's not there?" they're like, "she's not here and we've been calling her and she's not answering." >> reporter: thing was, jessyka was never late. missy tried calling her. no answer. panicked now, she ran to her car. was jessyka at home sick? >> so i was calling her all the way over there. and i was thinking, "i don't know where she's at." and then i started to think really bad things. maybe she was in a ditch somewhere passed out. maybe she was -- a really bad car accident. >> reporter: but you knew it was something bad? >> i felt something was wrong. so i get over there and her car's in the driveway, so i'm relieved. and i'm like, okay, she's here. she's not in an accident. but why isn't she answering the phone? >> reporter: the door was locked, so missy used her key to let herself in. >> i walk in and her house is really dark. i can't find her. and it's like, you know, everything is dark, so i don't know where i'm going. and the bathroom is, like, the first door on the left. and the door was closed, but i hear water running. and i'm like, okay, maybe she just used the bathroom. i opened up the door and i turned on the light, and she was in the bathtub. the water was running. water was up to her nose. she was in there like this. she had something in her hand. it was a phone cord and i didn't understand where that came from. i started screaming. i had my cell phone so i called 911. >> 911, do you need police, fire, or rescue? >> my daughter's dead in the bathtub. >> uh -- hold -- i don't understand a word you're saying. what's going on? >> i just found -- i just found my daughter dead in the bathtub. it looks like she slipped, and i don't know how long she's been there. >> i drained the water thinking that could help her. but she was already gone. >> reporter: you could tell? >> i could tell. she was blue. her face was -- a really weird pattern on her face. it looked checkered. but her body was still, like, a normal color. >> reporter: i can't imagine that. >> it was horrible. it's like a nightmare. i still see it. like, one of the worst feelings in the world when you can't help your daughter because she's gone. >> reporter: by the time jessyka's father, harry, got there -- >> there was a policeman in the driveway. >> reporter: and not far away he found missy, a wreck. a mess. >> i hugged her. what's going on? what do we know? don't know anything. >> reporter: had she slipped in the shower? >> he thought that at first. but i saw that mark on her neck and the cord in her hand. and i just didn't think it -- it sounded right. there -- she shouldn't have had her phone charger there. her phone wasn't there. >> reporter: so you didn't know what to think? >> i didn't know what to think. i was devastated. i wasn't even thinking at that point. >> reporter: first responders, trained to keep an open mind, weren't sure what to think either. >> it wasn't an obvious homicide. they didn't know if it was a medical emergency because we find people like that that have suffered a stroke or heart attack or something in similar kind of situations. so they really didn't know what they had. >> reporter: homicide detectives derek mois and ryan davis. >> i do a cursory walk through the residence. they show me where jessyka was at. she's in the bathtub. and oddly enough, her clothes were in the bathtub with her. >> reporter: but not on her? >> not on her. nope. they were laying near her feet. the couch in the living room had blood all over it, so my initial reaction was maybe there was some sort of medical emergency that occurred on the couch, she had gone to the bathroom maybe to clean herself off and had collapsed and succumbed to whatever medical emergency she was having. >> there wasn't any obvious signs of trauma on her body. >> she had a small bruise on the side of her neck. it didn't look like any sort of a -- >> reporter: could've gotten it any way? >> yeah. it didn't look like she was assaulted. >> reporter: but there was something off, too. didn't quite look right. they decided to treat it like a homicide. >> because you only get one chance at this. and so if you go in and you go guns blazing and you're trying to rush through things, you're going to miss things. >> reporter: the csi people arrived, used a laser scanner to quickly take billions of measurements and create this virtual representation of jessyka's house. 3-d, so more accurate than any photo. and then they removed jessyka's body. and, yes, detectives could see homicide was the right call. >> when we were able to actually look at her eyes, it was fairly evident that there'd been some sort of a strangulation and an asphyxiation at the very least took place. >> and one of the things we noted right away is that she had longer fingernails. and one of those fingernails was quite evidently bent back. and we knew that there was a chance then that if she had fought back against her attacker, there was potentially dna there. >> reporter: the next day the autopsy confirmed that jessyka had indeed been strangled to death. >> there was a slight ligature mark around her neck but it was disrupted, and it almost appeared as though that there was possibly a hand -- >> her hand maybe, trying to -- >> -- trying to pull, so the ligature marks were kind of intermittent. >> reporter: and one more thing the autopsy revealed, she'd been sexually assaulted. >> the first thing that goes through your head is why, how, who? i mean, everybody is a suspect and nobody's a suspect. that's -- who could've done this? why? >> reporter: she have any enemies? >> none that we knew of. >> coming up -- the man in jessyka's life and their volatile relationship. >> she would call us, like, every other week. "can you come out and get me? me and john had a fight." >> and then did a facebook post put her in danger? >> she just put out there that she was home alone. and she did it without even realizing. n my windshield crack. the experts at safelite autoglass came right to me... with service i could trust. right, girl? >> singers: ♪ safelite repair, safelite replace. ♪ at fidelity, your dedicated advisor will work with you on a comprehensive wealth plan across your full financial picture. a plan with tax-smart investing strategies designed to help you keep more of what you earn. this is the planning effect. (tiger) this is the dimension of imagination. designed to help you keep more of what you earn. ♪ ♪ >> reporter: there's nothing better than a close family and friends who are like family. missy and harry nelson had it. three kids, kids' partners, grandchildren. until. until the morning they found their beloved eldest child, their jessyka, just 28 years old, dead in her own bathtub. but who was she? detectives needed to know and so did we. >> everybody loved her. very bright. both my girls were really smart. >> very smart. >> reporter: jessyka was ashley and matt's big sister. >> she was very outgoing. she just always wanted to have fun. but, you know, the older we got, the more she was kind of like another mom to us. and, you know, she would always be there. even if we were fighting, if we needed her, she was there. >> reporter: big sister to the whole extended family, her cousins, her close friends who were more like siblings, her siblings' close friends who were more like relatives. >> she was always really nice to everybody. >> reporter: laura wonder had been a friend since grade school. >> she just wanted to have a good time. she was just kind of -- i wouldn't say crazy, but she just -- >> reporter: goofy? >> -- was kind of goofy. she did whatever she wanted to do. >> reporter: and that held true in her choice of men. her first serious boyfriend was him. >> with his tattoos and stuff. it was, like, he seemed to be something that she would have been into because she had a few tattoos as well. >> reporter: his name was john mcdowell. he and jessyka were good together and sometimes not. >> she would call us like, what, like every other week. "can you come out and get me? me and john had a fight, and i'm not staying out here." so we'd drive out there to missouri valley. and a couple weeks later, they're -- she's back out there again. >> reporter: a year in, there was still no wedding. but there was a baby, dominick, dom. >> i just remember, you know, everyone was so excited, wanting to meet him. >> she loved him, and i think it was just an instinct she had to be a mother. she wanted to do the best for him she could, and that drove everything else. >> reporter: and then one day -- dom was still quite small -- it all seemed to come apart. >> and they were doing okay. till he left her a voicemail. >> by accident. >> reporter: an unintentional voicemail. and the message that was left was, well, bad, very bad. >> talking to friends. he didn't know he left her a voicemail telling her that he -- he slept with another girl. and then that was it. she was done. >> reporter: whoa. >> so i helped her move that day. >> reporter: she must have been so upset. >> she was. she was devastated. >> reporter: to get an accidental voicemail from the guy who -- the father of your baby. "i slept with another woman." >> kind of bragging about it. "you should have seen the one i was with." >> reporter: and that's why jessyka elected to be a single mom. better, she decided, to concentrate on her little boy, the center of her life, dominick. >> she did everything she could for her son. just to try to do it right. got to work, pay bills. i have things i want him to have, so i need to pay for those things. and she'd work -- >> reporter: so she worked? >> two to three jobs sometimes. >> reporter: how does a person even do that? >> i have no idea. >> she worked at the first national bank. >> reporter: she liked that job? >> oh, yeah. >> she liked -- she loved it, >> that was her dream job. >> reporter: by then jessyka and dominick lived in the little house on the north side of town. >> it wasn't very big. but dom had the bigger room. and she's like, well, he has more toys, and his bed has a slide. and i'm like, he has a slide? and she's like, yeah, he needed a slide. i'm like, yeah, he -- sure, he needed a slide. it was just -- she gave everything up for him. he was her world. >> reporter: in fact, jessyka's last words on facebook the night she died when dom was at his dad's were, "i am such a mess when dom is gone." >> she had lost the remote and thought it was the worst 15 minutes of her life. >> she was lost, yeah, without dominick. because he could find the remote. >> reporter: but -- >> she just put out there that she was home alone. and she did it without even realizing. >> reporter: so if anybody was following her, they'd know. >> yeah. >> they'd know. >> reporter: but, of course, someone was following her on facebook. maybe quite a few someones. but finding the one with evil intent? not so easy. >> investigators start the search with jessyka's ex and soon hear some troubling stories. >> she would post pictures and if she's around with a guy even though they're just friends john you could tell he was a little like who's that? >> her sister ashley's ex raises eyebrows too. >> he threatened to take out my whole entire family to get custody of our kids. >> wow. when evil intent continues. reporter: word of jessyka nelson's death spread quickly, if incoherently, among her friends in omaha. >> i got a phone call from a mutual friend of ours. and she was so hysterical, i couldn't understand what she was saying. and i thought she said that dom had been killed. so i got off the phone with her and i called john, and he said, "they found jess dead." and it was just unreal. you just couldn't believe that. >> reporter: laura's friendship with jessyka had drifted a bit after high school. but by 2015, it -- well, it was a little unusual. laura and jessyka both had babies with john. laura dated him first, but it was after she broke up with john that her son christopher was born. and that was not long before jessyka got pregnant. >> i found out when i was six months pregnant with our son that him and jessyka had been dating or just started dating. unaware that me and her knew each other. so, both of us found out from him she's dating him and i have a child with him. so. it was kind of like a surprise to everybody. >> what kind of surprise was it in. >> i wasn't too happy about it. >> reporter: two women, two children. one man. >> i wanted to be mad at her and i couldn't because she was just too nice. >> reporter: anyway, pretty soon john was no longer in the picture for either of them. and then, as single mothers, laura and jessyka reconnected so their sons, half-brothers, could bond. >> our kids met each other and they got to play together. >> reporter: now her friend was dead, and the father of both their sons was sitting in the police station answering questions. >> when was the last time you were actually at the house? >> i -- i couldn't even tell you for sure. it's probably been three months. >> so when did you actually last see jessyka? >> when she dropped my son off last night. >> reporter: which meant john was the last known person to see jessyka alive except for the killer. unless he was the killer. detectives brought in jessyka's family members and friends and questioned them all about john. >> i think everybody kind of had their own impression of jonathan. >> reporter: and some of those impressions were not flattering. >> she would post pictures when she was out with friends, and if she's around another guy, even though they're just friends, john -- you could tell like he was a little like, "who's that? why are you with him?" >> jealous type of thing? >> yeah. >> did jessyka trust john? >> no. >> no. >> i know she was planning on filing for sole custody of dominick, because she was just tired of it and half the time when it was john's time to take him, he refused. >> they had these fights over dominick, over custody, over money. jessyka was routinely upset with him. >> reporter: john seemed to be trying to minimize those issues. >> do you have issues where you're at each other's throats or anything like that? >> no, no. the biggest thing that we might fight about is she's like, "you have a pair of shorts that i bought him two weeks ago and i haven't got to see them since i sent him to your house. you need to find them." >> okay. >> reporter: after a few hours of questioning, they let john go with a warning. he was suspect number one. and they kept an eye on him as they investigated other men who'd crossed paths with jessyka. >> we were interested in any male party she had recently been introduced to, anybody at all that could have been showing interest in her, communicating that with her via social media or any other means that maybe seemed kind of unwanted. can you tell me is there anybody that she's seeing like right now or she'd been seeing up until recently? and i'm talking about even casual hook-ups. one in a great while hook-up. anything at all? >> i know her last hook-up was with an old high school crush that had came back to town. he doesn't live here. he was a high school crush and he's in the military, so when he was home on leave she hung out with him for a few days, but then that was it. he was gone again. and i know she stayed over there once. >> reporter: detectives looked into his whereabouts the night jessyka was killed, and he was nowhere around. couldn't have been him. thing was it had to be someone close. someone she knew or trusted. someone with a key, maybe? after all, there was no forced entry, but the door was locked when jessyka's mother arrived in the morning. then her family told police about someone who'd been violent toward jessyka's sister, ashley, just a few days before the murder. >> i was going through a divorce. and my ex was not so nice. he'd threatened to take out my whole entire family and then myself just to get custody of our kids. >> reporter: wow. >> and the week before that, he physically assaulted me. >> he had pinned her on the floor and had left bruises on her arm. >> reporter: he'd been arrested, was facing charges for domestic assault. a man who'd been violent, who'd threatened family? detectives checked out his alibi for the night of jessyka's murder, but they also went looking for anyone else who might have had access to jessyka's home. like maybe some spurned lover. but apparently there weren't any, spurned or otherwise. >> everybody, when i asked that dating question, they would say that jessyka often referred to the only man in her life as dominick. and her other man was her job. and that's all she wanted to concentrate on, was her work and providing for dominick. >> reporter: but sometimes jessyka had friends over for saturday night gatherings when dom was at john's. and the last one, maybe ten days before she was killed, came with trouble. >> jessyka was freaking out next to me. she was like, "are they doing a drug deal in the house?" >> coming up -- >> you find all kinds of stuff on people's cell phones. >> oh, my gosh. yeah, absolutely. >> investigators discover odd text messages on jessyka's phone. >> there was just something weird about them. maybe we need to figure out who this person is. >> when "dateline" continues. b♪ unlimited cashback match... only from discover. no one can deliver your mom's homemade short ribs. for starters, your mom doesn't have a restaurant. if she did, it would be impossible to get in. she'd become famous overnight. she'd get talked into franchising everything. and at that point, they wouldn't really taste like your mom's short ribs. no one can deliver your mom's homemade short ribs. that's why instacart helps deliver the ingredients. cough cough sneeze sneeze... no one can deliver your mom's home[ sneezing ]ibs. needs, plop plop fizz fizz. alka seltzer plus cold relief. dissolves quickly. instantly ready to start working. so you can bounce back fast with alka-seltzer plus. now available for fast sinus relief. hello, here are the top stories at this hour. people in france paying respects to the 27 migrants who drowned crossing the english channel. it was a deadliest accident in the english channel on record. three children and a pregnant woman among the dead. 52 people in russia lost their lives after a blast in a coal mine. officials believe it was a methane explosion. they declared three days of mourning. back to date line extra. >> reporter: it was a week before they could have a funeral for jessyka. a small, sad service for family and friends is what they expected. but it wasn't small, not at all. >> it was overwhelming. just to see that that many people knew her or at some point had cared enough to show up and say, "hey, we're sorry." >> reporter: and some of the young men vowed revenge as they wore their "justice for jessyka" bracelets. her brother matt, her brother's best friend, also named matt, who'd once lived with them, who knew jessyka like a sister. >> he was with us throughout the whole thing. >> reporter: like another son? >> like another son. you know, just, you know, "what do you need help with?" people would bring over food. he's there helping us carry it in, you know, that kind of thing. >> reporter: and there as well helping out, grieving, was john mcdowell, jessyka's ex. he may have looked the part of a tough guy, but police had checked his alibi. he could not have been the killer. >> we were also able to look at his cell phone locations. and they were exactly where he said he was. at no point did his phone ever put him anywhere near jessyka's house. >> reporter: john did not kill jessyka, and when he first learned she was dead -- >> i just felt completely lost. i was instantly trying to figure out how i was going to tell my son that his mother, which was -- that was his world, was no longer here, and i didn't know what to do. >> did you do it that day? >> i did it that nite. i called her parent ts and asked them what should we do. how did they think i should approach it. and explain to him. and we decided that me and my parents and siblings. her parents and siblings. we got together as a family. and explain it to her. >> who did the talking? >> i did. >> can't imagine. what do you remember most about the conversation? >> he didn't understand. he thought she was still going to pick him up. >> that tugs at you. >> yeah. still does. >> reporter: he tried. but even at jessyka's funeral her son, then just 6 years old, didn't seem to comprehend. what was that like for you? >> it was horrible, especially with her being right there, and he still wasn't comprehending that she -- that she wasn't with us anymore. >> reporter: that was when the detectives were tracking down -- well, they didn't know who. the sister's ex, the guy who'd been charged with assault, had a solid alibi. but what about the men who'd attended jessyka's small parties? one party in particular. >> one of her friends invited her boyfriend. her boyfriend invited some of his friends. those friends invited others. so as this get-together kind of went on in the evening, more and more people were showing up to jessyka's residence whom she didn't know. >> reporter: what does that do to an investigation when you've got -- >> it opened our suspect pool up quite a bit. >> reporter: especially after friends told detective mois that jessyka thought something illegal was going on at her party, asking them -- >> "are they doing a drug deal in the house? this is not okay." >> i just know that people came outside and said, "hey, that guy there, he's got pills if anybody needs any." >> so i want to know exactly who invited this guy to jessyka's house that night. who thought that would have been okay to do that? >> reporter: the answer complicated matters even more. friends told detectives that the man who'd invited the drug dealer also tried, at the party, to initiate some kind of sexual encounter with jessyka. >> he was in the bathroom and she went to go grab a towel and says, "hey, can you grab me a towel?" and he like let her in the bathroom. and then he was like, "uh, do you want to stay in here with me?" and she was like, "no, i just want a towel." and he like -- i guess she said he had, like, tried to close the door and all that stuff. and she's like, said "no," opened the door and walked away. >> reporter: so now they had to track him down. him and every male who attended the party. how long did you spend on this? >> we spent several weeks. that's all we were doing is attempting to identify these people, locate them, interview them, and go through the same vetting process as far as getting a timeline and alibiing them, as everybody else. >> and we were taking dna samples from every single person we talked to. >> reporter: at the same time, they asked one of their tech investigators, nick herfordt, to look for clues in jessyka's cell phone. you find all kinds of stuff on people's cell phones, i bet you. >> oh, my gosh. yeah, absolutely. but what's actually remarkable about this one when you say all kinds of stuff, on this one it was pretty much just one thing on there and it was just pictures of her son. >> reporter: this kind of stuff. >> her life just completely revolved around him. >> reporter: but there were text messages, too. lots of them. and some were pretty interesting. >> one of the last people she was communicating with, someone was named matt kidder. >> reporter: matt kidder? he was the friend, more like a son, who'd grieved with the nelson family and was like a second brother to jessyka. they'd always had an easy, teasing sort of relationship. so, of course, they'd texted each other. but officer herfordt didn't know any of that when the texts caught his attention. >> there was just something weird about them. just the way that he was -- he would be constantly asking her, basically, out to do stuff. he would say, "hey, do you want to go bowling?" and she would be like, "you know what, i've got to clean up the house." and then he would be like, "oh, well, i can come over and maybe help you clean up the house?" and then she'd reply, like, "oh, you know what? i'm almost done. don't worry about it. and now i'm really tired. so i'm just going to go to bed." something like that. and it was like this over and over. so i talked to the sergeant who was in charge and said that maybe we need to kind of figure out who this person is. >> reporter: jessyka's friends and family said that sort of back and forth was quite typical of their relationship. >> it was just like brother and sister type of thing. you know, he'd get smart with her. she'd get smart back. and they'd go on their way. >> reporter: so apparently, nothing to see here. but of course, detectives had to dig a little. who was this matt kidder, whom the nelsons loved like their own? >> in the interrogation room matt opens up to police revealing he feels guilty he didn't stop the killer. >> i feel like i was there and i could have done something if i drove by that night or if i had known. >> when "dateline" continues. feel stuck with credit card debt? move to sofi and feel what it's like to get your money right. ♪ move your high-interest debt to a sofi personal loan. you could save with low rates and no fees. earn $10 just for viewing your rate and get your money right. ♪ >> reporter: a murder investigation is often a collection of stories. whodunit stories, yes, but also love, loss, regret. john mcdowell was innocent. but he didn't feel innocent. >> the only thing that went through my head is that it really, it was all my fault, because if i would have never messed up and if we would have never split up, then i would have been there to protect her. >> reporter: i think you still feel that way a little bit, don't you? >> yes, sir. >> reporter: does she intrude upon your thoughts a lot? >> yes, sir. >> when i look at my son. he looks just like her. >> what's the feeling that comes over you when you think about her and the fact she is gone and won't come back? >> it's not fair. >> reporter: so many stories, witnesses, family, friends of the victim. like matt kidder. >> when i got the call i walked out the room to make sure the sky wasn't on fire because i couldn't -- "no, no, jessyka wouldn't be dead." >> reporter: when detective davis interviewed matt, he encountered a man still apparently grieving. >> she had a really good heart. good mother, good friend. i don't think i ever heard her not put herself out for someone in need. >> reporter: and so davis was sympathetic, and matt opened up, talked about his brotherly, teasy sort of relationship with jessyka. >> me and jess, we've always had a relationship where we have, like inside sexual innuendo jokes even though we never had an interest in each other like that. i've kind of always enjoyed that, being able to joke around with somebody, you know, we know it's never going to lead anywhere so everything's on the table. >> reporter: and like brother and sister, he said, they'd sometimes get physical in a playful way. >> we'd fool around a little bit, but -- >> how do you mean? >> oh, just kind of like she'd pinch me, i'd poke her in her side. i mean, just like teasing, sibling teasing i guess you could call it. >> kind of like flirting, though. >> not quite like -- i don't know. maybe. i didn't consider it flirting. and it wasn't like -- and as far i know, she has never been interested in me. we were just friends. >> reporter: and after jessyka was murdered it was matt who vowed to take revenge and told detectives he felt so guilty for failing to protect her. >> i would do anything for my friends. i would die for them if i had to. it's just, i know it's stupid, i've talked to her mom because she's kind of sort of going through the same thing. i shouldn't put it on myself, but it's -- i feel like i was there and i could have done something if i had drove by that night or if i had known. >> reporter: after all, he was at work that evening close by. so, he said, he struggled with regret, even as he tried to figure out what happened. >> i have an overactive imagination or brain or whatever you want to call it. >> reporter: whoever did it, said matt, must have been waiting to find her home alone and must have seen her facebook post, the one about her son, dom, being away that night. >> that has to be a million shot to get there without dom being there. like if they were watching her facebook feed to go in, it's like somebody had to have been watching the house for a while to know that she was 100% alone there. >> reporter: and maybe, he said, maybe it was more than one guy. >> i'm a fairly strong guy. i have weaknesses, my body is pretty [ bleep ] up so -- but she can kick my ass. so it just doesn't make sense for one person. >> reporter: he knew something about bad guys. he'd spent some time in prison, he said, for something he didn't do, attempted sexual assault. >> i was dating a married woman, and when i broke up with her she called the cops and reported me for rape. >> reporter: but she lied, he said, a false accusation. and the nelsons supported him. >> this guy somehow got railroaded over this. >> reporter: so this poor kid had some kind of consensual relationship? and then afterwards -- >> yeah. >> reporter: -- instead of getting in trouble for it, she blamed him and accused him of rape? >> yeah. >> and i even knew somebody that knew her. and she told me the same thing, that she was always up to no good. >> reporter: so after matt got out of prison, the nelsons celebrated with him and his family. after all, his dad and harry nelson had been best friends for decades, just as he was best friends with jessyka's brother. >> they've had my back for as long as i can remember. >> reporter: after jessyka's death matt provided a sample of his dna and said of course he'd been to jessyka's house. so if his dna happened to turn up there, well, perfectly innocent reason for that. >> i pretty much bleed in everybody's house i go to because i get bored and either i pick at a scab or cut myself on something. >> reporter: but if they were looking at him as a suspect, they had the wrong guy. >> i wouldn't be able to look them in the eye if i had did this. i wouldn't be wearing justice for jessyka on my wrist. i wouldn't be sharing her picture on facebook, looking for the [ bleep ] people who did this. i'm not built that way. >> reporter: no, matt kidder was virtually a member of the family. >> because we're all suffering. i feel better being around their family sometimes. >> reporter: he couldn't have killed jessyka. could he? >> coming up -- stunning and heartbreaking. what this woman has to say about jessyka's murder. >> it never should have happened. >> because you'd already warned everybody about him. >> yep. >> what her story will mean for the case. when evil intent continues. ♪ ♪ cases of anxiety in young adults are rising as experts warn of the effects on well-being caused by the pandemic. ♪ ♪ ♪ ♪ ♪ ♪ ♪ ♪ >> reporter: matt kidder, the young man who was like a brother to jessyka nelson, like a son to her parents, was sitting in the police station three weeks after jessyka's death. >> do you think i consider you a suspect? >> i think you consider everybody a suspect at this point. >> okay, but specifically do you think i consider you one? >> i hope not. >> reporter: but by then the omaha police did see him as a suspect. they knew that matt checked facebook the night jessyka was killed, would have seen the post that revealed she was home alone. they had discovered that matt's cell phone was at or near jessyka's place for 17 minutes that night. >> reporter: police tech experts oscar dieguez and nick herfordt. >> so right now, it's about 11:00, and you're going to see a couple more activations where he's still at work. and right there -- and then all of a sudden it switches. >> reporter: and that's at her house. >> yes, that is directly in the area of the house. >> reporter: and there was more. the detectives had noticed a crescent-shaped cut on matt's hand. this could have been made by jessyka's thumbnail bending back as she defended herself. >> the fingernail swabs from her hands. and the blood in the house. >> he provided his dna sample. during his initial interview. we immediately brought that in. and they found his dna under that nail and on the cord she was strangled with. >> 100 parse match. 100% match. >> so now detective davis played his hand. >> i think you were there when this went down. and i think you had something to do with it. >> reporter: and matt exploded, a stream of loud and determined denials. >> i didn't kill her. i don't know who did it. i wasn't [ bleep ] there that night. i wouldn't be able to watch my uncle harry basically collapse over the body of his daughter at the funeral if i had done this. somebody's murdered my friend, and here you are trying to accuse me of it. you arrest me for something i didn't do, especially on this, it's going to destroy her family. >> reporter: brenda beadle was lead prosecutor. >> he was narcissistic, and he is a sociopath. and so if you were just watching that interview without knowing the evidence we had, you might scratch your head and go, "do you think we have the right guy?" because he was so convincing. >> reporter: but police believed they did have the right guy, and they arrested him for the murder of his lifelong friend jessyka nelson. >> stand up, man. >> i'm not going to jail for this. >> it's not up to you. decision's been made. so i need you to stand up. >> it's the wrong [ bleep ] decision. >> that's something you can take up with your attorney. right now i need you to stand up because you're leaving here. okay? >> reporter: now it was time to tell the nelsons. >> he said, "we have made an arrest, and we have arrested matthew kidder." my head hit the table. >> we didn't get into details on the evidence. we made sure they understood there's no doubt in our mind we have the right person in custody. and the only way i can describe is they were in disbelief. very quiet. i don't think anywhere in their mind did they believe that somebody so close to them could have been responsible for taking their daughter away from them. >> reporter: missy and harry gathered the family to tell them. >> i said, "look around. look at everybody here. who's one person that would probably be here, but isn't?" and my son matthew kind of raised his eyebrows like, "oh my god, no." >> reporter: up until that moment matt kidder had been matt nelson's best friend in the world. the one he trusted implicitly. the one who would never, ever betray them. and here they were. >> everyone who was there broke down like just bawling their eyes out. >> reporter: as matt kidder waited in the local jail, evidence piled up. he talked to his father on the phone, recorded, of course. >> i think she fell asleep on the couch after i left and somebody came in behind -- >> after you left? you were never there. >> dad, my phone puts me there. >> huh? >> dad, my phone puts me there. >> oh. >> it's changed now from the 169 times he denied being in the house, yelling at the detective, very sternly denying that he was even there. that was big. >> reporter: there was more. he got chatty with his cellmate, told him the whole ugly story. this is prosecutor beth beninato. >> this informant, the details he gave us, they were accurate, from walking into her house, head-butting her, which would explain the blood we saw and the blood patterns on the couch cushions, to the sexual assault itself, to the things that she said, to the injury on his hand and the injury on her finger, to the cell phone charging cord. this informant gave us a view into what jessyka went through. >> it was about power, control, and i think being rejected by her via text just made him angry. he's a very angry individual. >> reporter: i guess, or was that in a weird way his turn-on, that the more he's rejected the more he needs to have that power and control and that's kind of part of the buildup or something? >> uh-huh. >> we think so. >> reporter: which brings us to this woman, patricia springborg, the woman who accused matt of rape. remember, he went to prison, attempted sexual assault, but convinced the nelsons she was lying. it was no lie. and when patricia heard about jessyka? >> that's the hardest thing for me, because it never should have happened. >> reporter: because you'd already warned everybody about him. >> yep. >> reporter: her experience with matt at first was not unlike the nelsons'. >> he wormed his way into our family and none of us thought he would do anything like that. >> reporter: so he was actually a new friend of your family, too. >> yes, yes. i met him through my oldest daughter. >> reporter: wow. >> yep. my husband taught him how to drive his truck, you know, things like that. things that you would do if we had a teenage boy. >> reporter: sure. and then one day he caught her alone at home, and he grabbed her neck and tried to choke her. and she, fearing he would kill her, stopped struggling and discovered something revealing about matt. >> from what i could tell, and with my situation, is the violence and stuff is what got him. >> reporter: yeah, because when you relented it obviously wasn't a turn-on for him anymore. >> uh-uh. >> reporter: and if she hadn't given in? >> i wouldn't be here. >> reporter: you would have been in jessyka's place? >> yeah. this shouldn't have happened to that girl. >> reporter: no, it shouldn't have. >> and she's got a little boy, and it just shouldn't have happened. that's why after everything that happened, when the prosecutor asked me if i would testify for them, damn right. >> reporter: and she did. and there was one more thing. the police had seized matt's laptop when they arrested him, and what they found, well -- >> i've seen some weird stuff but nothing like this. it was a lot of rape videos and torture videos and just, like, the combination of them. i mean, it let us know basically his intent and his mindset, because what he ended up doing is basically recreated one of these kind of videos that he likes in real life. >> reporter: in real life. >> where he stormed somebody, assaulted them, killed them and then left. >> reporter: matt kidder did not testify, but his defense said all the evidence, dna, cell phone tracking, the cellmate's story, all had innocent explanations. and besides, they said, he wasn't the killer, plain and simple. but the jury deliberated just 41 minutes before convicting matt kidder of jessyka's murder. he was sentenced to life in prison. >> i think for myself it's hard not to -- my mom was a single mom. it's hard not to be personally tied to it. in some way. it certainly affected me and a lot of us. here you're at home and where you should be the safest in life. for somebody so devoted to her son, i don't know. >> she was innocent. she was innocent. she didn't put herself in a position at all -- >> nothing she did brought this to her door. >> betrayal. yeah. why did you want to do it to her? >> are you glad you know what happened. >> kind of. it still haunts me. >> it still hurts. it's painful. >> we're glad to know that especially now that he's where he is. he can no longer hurt anybody else. >> right. >> just the monster within the family has been taken away. the nelsons, of course, still miss jessyka terribly. and dominick? lives with his dad, john, now and also with laura and his half-brother, christopher. after jessyka's death laura stepped in to help out as much as she could. >> we were over there all the time with dom and john and the kids all playing together, and it was just one day after the next after the next. and you just fall together. i mean, it's the one good thing that came out of this tragedy. dom has a whole family, and he's so happy about that. you know, he says, "i got a mommy in heaven and i've got a mom here." >> reporter: in time laura and john got engaged. and the nelson family grew by a few more. just one empty place. but you never fill the hole in your life, do you, when you lose a child? >> no. >> no. >> reporter: how often do you think about jessyka? >> every day. >> every day. i think about her more than anybody does. everybody said she was a little me. when i look at myself in the mirror. i see her. i want to make her proud. carry on without her here. loving person she had a heart of gold what happened to this woman? my job is to be a truth teller and seek out the truth >> her case was a missed year for year. his mom with a tender heart, and tough as nails career. she was part of the sheriff's department she found in a sense of purpose her