>> is this guy dodging us? >> he kind of selected her as his victim? >> correct. >> of course, the bottom of the big site there was a damaged iphone. >> it looks like maybe clothing. it was just a sinking feeling, really. >> i just ripley this one night i had with her and i just want to grab her and say don't do it. don't go. >> hello and welcome to "dateline". college student mackenzie lueck was diving into adulthood, eager to find her path. her family and friends knew her as fun, responsible and always careful. then one night, mackenzie vanished. a trail of electronic clues helped investigators retrace her steps and exposed a dark underworld were evil was hiding behind webs of lives. here's keith morrison with "the waiting car". >> our minds have a curious way of deceiving us. we sense something off, something wrong. even terrible. and yet, something in the brain wants to believe the worst didn't happen. kennedy stoner knows that feeling well. >> i was kind of pushing away from my gut instinct. i'm not really sure why. i never imagined this ever happening to one of my friends. >> i wouldn't think you would want to imagine it? >> no, or anyone that i know. so, my mind didn't go there. >> so, she told herself it would be fine, as she reached out from her home here in salt lake city, utah. messages to her friend, mackenzie lueck. >> i saw that she was an opening my snap chats and i texted her. i didn't get a text back. and this is stupid, but i was kind of wondering if she was mad at me for something. >> the mind once a simple explanation. after all, she knew her best friend was grieving. mackenzie's grandmother had recently passed away in california. >> i know she was heartbroken over that and so was the rest of her family, because they were all very close. >> she went to the funeral? >> she did. she left utah, she went to the funeral. so, i was thinking maybe she just took a few days off social media or something. >> mackenzie's parents though, had heard from her either. after three days of escalating fear, mackenzie's that made that most dreadful phone call to the salt lake city police department. >> yes, i'd like to get -- if possible, have a wellness check down on my daughter. i've been trying to get a hold of her and her phone just tends to go to voice mail. i was just wondering if i could have somebody maybe go by her house and check on her? >> the story mackenzie's that told was this. on the night of sunday, june 16th, 2019, mackenzie had boarded a flight from los angeles back to utah. arriving in salt lake city around 1:35 am, monday. at 2:01 am, she texted her mom to say she landed safely. after that, three days of silence. to patrol officers went straight away to mackenzie's town house. her car was in the driveway. that was a good sign. repeated knocks at the door, however, went unanswered. peering through a window, the officers saw nothing. not a soul around. they called mackenzie's that to report the news. and next, the officers phoned mackenzie's friends, bus and professors. none of them had seen her. all reasons why at the end of this unsettling day, mackenzie's case was referred to a place that sounded very serious indeed. the salt lake city police departments on the side squad. >> we get a lot of missing persons cases in salt lake city. >> lieutenant todd mitchell was the units chief detective. >> so, i tried my best to sift through those and find the ones that raise that here on the back of your neck, for the lack of the backer term. and this raise the hair on the back of my neck. so, that's why i decided, yes, we need to take action now. and at least are on an issue investigation into it. >> through three told, most reports are easily resolved. the missing person may have simply lost their phone or just decided to take a break from some family drama. but that did it appear to be the case with mackenzie. the relationship she had with her mom and dad would be the envy of most parents. they >> were always kentucky each other. they sent silly text back and forth on a daily basis. >> detective and tiffany sayes levitate missing person investigation. even though their specialty was murder. >> we are usual homicide investigation, we start, there's a dead party. we were starting with something. we have a victim and we're moving backwards. in this case, we started with nothing. >> first action, sayes and wiley was to pull the salt lake city airport footage from the night of mackenzie's disappearance. and sure enough, there she was. >> so, there is nothing out of the ordinary. we are able to see her come off the terminal and we followed her all the way down to the baggage going, where she picked up her luggage. >> seem perfectly normal, fine, casual? >> yes. nothing out of the ordinary that we can seattle. >> the last clip shows mackenzie, like so many other passengers, casually getting into a car outside baggage claim. but the identity of the driver? a mystery. news of this police investigation quickly spread among mackenzie's friends. >> the second i heard about that, my stomach dropped. >> so, kennedy launched her own investigation. >> i went on facebook. i dropped pictures of us together and i said, she's missing. if you know anything, reach out to me. reach out, police. i >> thought she was still in california. until i saw kennedys message on facebook. >> ashley fine, another of mackenzie's college friends, put up her own facebook posts. >> and i tagged her in it and because i tagged her on facebook, some of her other family members reached out to me immediately. >> while family members? >> some of her distant cousins. one who lives here in utah and we started talking and messaging. and i said, you know, i have a feeling that she took a lyft share. i feel really strong that she did that. >> so if, you're worried that maybe something happened in that car? >> definitely. definitely. >> on her own ashley and her cousin called lyft and uber, to see even if either one of them had picked up mackenzie at the airport. >> and that's really when this began, because somehow they let it slip lyft did. that she got in me lyft that night. >> what did you do at that point? >> we contacted law enforcement about the lyft. >> a big break for sayes and wiley. because it gave them probable claws to serve lyft with a search warrant. >> and find out where her destination was, where she was dropped off, will time she was picked up? >> where did she go? so >> so, we were able to get the destination from the airport all the way up to north salt lake address and she was dropped off at hatch park in north salt lake, just before 3 am. >> a park? at 3 am? why would mackenzie come here? and just as important, why would a driver leave a young woman alone, burdened with luggage, at a park in the middle of the night? who would do such a thing? it was detective sayes to track down the driver. who she discovered, was not so easy to find. we >> were like, is this guy dodging us? >> coming up -- mackenzie's france have a terrifying theory about why she's missing. >> i assumed that the lyft driver abducted her. >> and here's one reason why. >> her last text message that we recovered was at 2:58, prior to her arrival arriving at the hatch park location. and that was the last activity ever we had on her phone. >> when "dateline" continues. ♪ ♪ just two pills for all day pain relief. aleve it, and see what's possible. there's lots of people who are confused about which medicare plan is right for them. hey, that's me. i barely know where to start. well, start here with me, karen. i'm a licensed humana sales agent. well, it's nice to meet you karen. i'm john smith. hi john. at humana we know you're unique so you have different needs from other john smiths. yeah, i've always thought so. and together we can find a plan that's right for you. great! i go to the doctor a couple of times a year and i have some prescriptions. but i'm never fully sure what's covered and what's not. with humana's all-in-one medicare advantage plans you get coverage for hospital stays, doctor visits and part d prescription drug benefits. all for an affordable and sometimes no monthly plan premium. do you have any more information? 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>> definitely. he did. he didn't seem like he had anything to do like this idol. >> because he had an alibi, a very good one actually. as soon as he dropped mackenzie off, surveillance footage at a nearby intersection capture him leaving picking up another fair, the daytime and location all confirmed by the tracking software on these lift apps. >> and he continue that throughout the night, and so -- >> you could eliminate him pretty easily based on the fact that he was elsewhere? >> very quickly, yes. >> she was smiling, she was in good spirits. >> mckenzie's lyft driver, told police and later us he remembered the we're to drop off location, even mckenzie commented on that he said. >> saying how it was odd to be dropped off in the middle of the night in a park. >> he says that he wasn't worried because someone with a car was there waiting for mckenzie. >> i unloaded her luggage, said goodbye and drove away. >> so who was that someone in the waiting car? the detectives were hoping they could identify him or her through mckenzie's phone records. and she had been texting a number with a two zero six area code right after the point her phone went dead. >> so, we were able to actually take that number run it through our little databases and it came back as absolutely nothing, it came back as nobody. >> and it could be some type of burner phone. so whoever that was did not want anyone to know? anyone in any official capacity to know who it was? >> yeah, it was pretty obvious at that point. >> but according to the lyft driver, whoever met mackenzie at the park, made no effort to conceal their identity from them. on the contrary. >> they seem to know each other. very well. i think all i heard was how are you doing, how is your trip, basic ratings. the situation seemed very safe. she knew the person that she was getting in the car with. >> did mackenzie caught a car with someone that she knew with, was both good and bad news? the good news, of course, was that it meant maybe mckenzie went off with a friend somewhere. the bad news? because there was now no proof of a crime, the detectives had lost their power to get any search warrants. >> we had lost our what we call probable cause, that a crime had been committed. >> just like that? >> just like that. >> just because of what the lyft driver said, suddenly you can't be getting warrants for things? >> correct. that was a hard part and it's slow down the investigation at that point, because we didn't have a crime to attached to it, it was still now a missing persons investigation. >> without a warrant the detectives were blocked from getting detailed phone records, which theoretically, would've shown cool mckenzie was texting. so who was this friend mckenzie met at the park? where did they go? >> investigators are about to uncover fresh clues that deepen this mystery, but also give mckenzie's loved ones a glimmer of hope. coming up. one place mckenzie wasn't missing was on social media. >> different people saying hey, i'm looking at her sights right now and it is showing that she is actively online. >> her bank account was active to. >> so we're hopeful that there could be further transactions on there so that we could find her. >> when dateline continues. hen dateline continues d better in the shower. and it turns out the general is a quality insurance company that's been saving people money for nearly 60 years. for a great low rate, and nearly 60 years of quality coverage, go with the general. i've been telling everyone... and nearly 60 years of quality coverage, the secret to great teeth is having healthy gums. crest advanced gum restore. detoxifies below the gumline... and restores by helping heal gums in as little as 7 days. >> so many questions. crest. the #1 toothpaste brand in america. why did mackenzie go to a park eight miles from home at 3 am, no less. who did she meet? it made no sense. to her friend ashley fine. >> i can't even believe she would meet someone at a park at 3 am. it's just so unlike. here >> it is? >> so unlike her. >> because mackenzie, like most of her sorority sisters, talked a lot about safety. i >> mean, i've been out with her a lot of times and she's always been extremely safe. she's texted me after going out at night and said, hey, did you make a home? are you okay? >> you had exchanged things just to keep each other safe? >> yes. >> ashley had met mackenzie almost four years earlier. >> she was a little bit shyer than most people would think she would be. but once you got to know her, she had a big personality. she could make anyone laugh. >> kennedy stoner also met mackenzie in college. >> her family doesn't live here so she was all on her own here. so, she got a job, she was going to school. she was checking off everything that a responsible adult would have on their checklist, i guess. >> mackenzie grew up near los angeles los angeles, el segundo, california. and she was raised in the church of latter-day saints. but when she came to the university of utah study kinesiology, according to actually, mackenzie did exactly remain devout. i >> know she was registered here in salt lake city, i heard she was never active. and that made sense to me because i think she wanted to find her own path. >> you saw her changing? >> yes. >> in recent times, didn't you? >> in what ways? >> i think she was trying to almost gain confidence and security in herself. she'd always write herself notes saying how she wanted to feel more confident, because i think she realized she was really shy and she wanted to be more outgoing and the people. and she wanted to explore dating and it might not be how everyone else thinks that dating should be. >> while ashley is getting at is that mackenzie was active on dating sites. so much so that by saturday, during the 22nd, the sixth day after mackenzie's disappearance, detectives had received several phone calls from some of the men mackenzie met online. namely to say they had nothing to do with her disappearance. >> i mean, nowadays that's how people meet people. so, while it was of significance because it gave us one more thing to look at, it wasn't this big, huge red flag either. >> so, was mackenzie off on a lark with a guy she met online? a hookup she wanted to keep secret from her devoutly religious parents? well, that certainly seemed far more likely than some sort of kidnapping scenario. >> she could've gone camping, or gone with a friend, where they would lose self-service and it wouldn't be out of the ordinary. >> but was they did some checking around that camping ideas seemed a lot less likely. bystander procedure, they locked up airline flight records and discovered mackenzie had been booked on a flight out of town to los vegas. so, maybe she was there. and meanwhile, the port detectives began to see activity on her bank account. and something else. >> different people saying, hey, i'm looking at her sight right now and is showing that she's actively online. >> so, maybe she was just fine. ignoring the office, or zoned out entirely unaware of it. >> so, we were hopeful. >> sure. >> because when people go missing, even if it's on their own accord, they're still going to be bank transactions or pink for stuff. so, we were hopeful that there would be further transactions on there so that we could find her. >> not far from the police station, kennedy and ashley hosted a rally to make sure everyone in salt lake city new to be looking for mackenzie. >> hey, guys, this girl is missing and we're looking for. she could be in danger. we think she's in danger. >> but was she? on sunday, during the 23rd, detectives learned mackenzie had a flight booked for that very day, traveling from las vegas to los angeles to attend a friend's wedding. >> she wouldn't miss that. so, we contacted los angeles police department and they had officers waiting for that flight to land. >> they waited for all the passengers to de-plane. mackenzie was not among them. then they learned this. it wasn't mackenzie who'd been logging into her social media accounts. that had been her friends. >> they obtained her email password and they were doing it to try to ruin things or anything, they were trying to go on there to monitor the sites as well to see if any information could come up. >> and the activity on mackenzie's bank account? >> it was the left transaction on the 17th and then an automatic payroll deposit from her work. >> and then the detectives got a tip from -- the sky. who, just maybe, could bring all of those blurry details into sharp focus. >> coming up -- >> i got on the computer and within an hour, two hours, i had found her profile. >> the world of sugar babies. i think >> we're living in a culture where it's much more accepted and embraced for women to be upset upfront about what they need and want. >> did know mackenzie what she was getting into? >> a lot of people who go into it are seriously so blind to the whole reality of what it is. >> when "dateline" continues. shingles? oh... you mean bill. he's been a real pain. again with the bill... what? it looks like a face. ...hearing about it 24/7 is painful enough... i don't want to catch it. well, you can't catch shingles, but the virus that causes it may already be inside you. does that mean bill might have company? - stop. you know shingles can be prevented. shingles can be whaaaaat? yeah prevented. you can get vaccinated. oh, so... i guess it's just you, me and bill then. i'm making my appointment. bill's all yours... 50 years or older? get vaccinated for shingles today. my hygienist cleans with a round head. so does my oral-b my hygienist personalizes my cleaning. so does my oral-b oral-b delivers the wow of a professional clean feel every day. don't settle. start your day with secret. secret stops odor causing sweat 3x more. and the provitamin b5 formula is gentle on skin. with secret, outlast anything! no sweat. secret. ♪all strength. no sweat.♪ >> texas abortion clinics canceled appointments are booked in the last two days, a u.s. appeals court reinstated texas a strict abortion law on friday night. abortions are once again prohibited after cardiac activity is detected around six weeks of pregnancy. german police are investigating cases of havana syndrome at the u.s. embassy in berlin. according to media reports, they said they had symptoms such as dizziness, nausea and severe headaches. now back to dateline. headaches now back to dateline >> welcome back to dateline, i'm natalie morales. where was mackenzie? the college student took a lyft to meet someone at a park at 3 am. but who? mckenzie was active on dating sites making police wonder if her late night rendezvous was a hook up, and her radio silence was intentional. now a tipster was about to share troubling details of his encounter with mckenzie shortly before she went missing. here's keith morrison with the waiting car. >> it was a few weeks before mckenzie vanished, a meeting at a bar, with this man rob joseph. >> she seemed like a very bright to bubbly girl friendly. >> they talked for more than an hour said robbed or she did while he listened. rob is a cop, which of course he told her. >> if you mention you're an ex cop in your piece i, everybody all of a sudden wants to tell you they're dark secrets or risky behaviors. >> it's not how people react, really? >> yeah. you would be surprised. people just want to tell you things that you don't want to hear. >> anyway. he only saw mackenzie that one time, he said. didn't get her phone number and -- >> i didn't offer my number, i usually don't get on my number. >> and that was that, he said. he didn't expect to see her again. but, just three weeks later. mckenzie was missing. rob said the friend who was with him at the bar that tonight made the connection. >> he just mention to me casually, that girl we met at the bar, that's the girl that went missing. >> of course rob remembered the student and the secret she revealed to him that night. >> i don't know whether she was seeking approval or just advice or recommendations -- >> how did she put it? >> she said she was on a dating site and looking for sugar daddies and i said to her which ones and she said seeking arrangements. >> seeking arrangement, a wet side designed to connect young women with prosperous old man. robert newell lot about dating sites, he is a p.i., remember? he figurative mckenzie was missing, that just might have something to do with it. >> i went straight home got on the computer and got on to seeking arrangement and within an hour, two hours i had found her profile. >> there she was, beach baby 96. >> what was interesting about her profile is that it was very authentic and honest. she wasn't really hiding who she was, she was pretty specific about -- 23 year old, grad student studying kinesiology, california girls. likes to drink wine, likes to go out, likes to travel, looking for somebody to do that with. >> a little bit more pg than some of them, maybe? >> yeah. >> soon as he founded he sent a screen grab of mackenzie's profile to the salt lake city police department. >> this was definitely another avenue that we had to look at, and track down anybody who might have been in contact with her. >> mckenzie appeared had car park to mental eyes information about her life. >> the plane ticket to los angeles, for instance had been paid for by man she had met through seeking arrangement, and a 300 dollar deposit to one of mackenzie's bank accounts? >> that was from one of her other dates that she had been on that she had received a payment from. and that was prior to her go bring over to her grandmother's funeral. >> her friend, ashley, said she didn't have a clue. >> i didn't know anything about her being on that side -- >> she didn't talk about it, it wasn't like a start a conversation? >> not with me. >> mckenzie spring kennedy wanted to avoid the subject altogether. but she acknowledged that seeking arrangement is well known on campus. >> this site is not unfamiliar to a lot of women and in women in college. >> everybody knows about? it >> every knows about the site. >> seeking arrangement was founded in 2006 by a self proclaimed nerd and mit grad name brandon weighed. he declined our interview request but in this 2016 today show story wade said he came up with the idea as a way to meet young women. >> the average sugar baby is roughly 27 years old, 50% of them are college students, they are ambitious, they are beautiful and they are on the website because they want to find somebody who is successful who will help them or spoil them. >> i think we're living in a culture where it is much more accepted embraced for women to be upfront about what they need and want. >> journalist mary ella moss novel writes about sex and culture, and sees sugaring as a form of female empowerment >> and, to hold power in a way that is opened that is less stigmatized that it has been in the past. >> so they see this as holding power? >> i see it is very powerful, yes. >> explain that a little bit. >> anytime you go into a relationship of any kind saying this is what i need and if you can't give me this i'm going to move on, it's a powerful thing to say. >> there is some debate about this, whether it actually empowers young women or exploits the innocent. >> i mean, a lot of people who go into it are seriously so blind to the whole reality of what it is, you know? >> like mckenzie, she had a seeking arrangement profile but unlike mckenzie, she told us that she was anything but a new be when we spoke to her in 2019. >> at the time the 20 something had been with a sugar daddy for six months, he was 63. do you mind telling me how much he paid you? >> my allowance is 1200 a month. >> she told us it took her a long time to find and arrangement. >> you have to fished through all of those guys who like, literally, say let's meet up at a hotel, have sex and i will give you money. and i'm like that's a prostitute. >> shades of gray could be confusing for anybody said it asia, let alone a novice on seeking arrangement. >> i've seen girls who have had sugar daddies they're not even the same person after. >> did you read a mackenzie's profile? >> yes i. did >> she came from a sheltered upbringing, would that have made it more dangerous for her? >> most definitely. going into it blindly is not something i would recommend. like at all. >> welcome to elects top sugar, in this episode, it's all about getting ready for your sugar date. >> seeking arrangement does make what they call let's talk sugar videos, they offer advice to novice sugar babies giving tips on everything from how to ask for an allowance, to what to pack in your purse. perfume they say, and pepper spray. >> not that you'll need it on your date, but, going out looking hot is always a risk. >> did mackenzie watch to the videos, we don't know. but one of her decisions said deja betrayed her lack of experience. >> why would you meet in the middle of the night, in a park? >> and there was something else, whether mckenzie did it or the person she met, we don't know, but remember right after the lyft driver dropped her off at the park, someone turned off mckenzie's cell phone. which happens to be contrary to seeking arrangement most important rule. >> you never want to get stuck fullest, that is your lifeline. >> mckenzie lost her lifeline, but before it went silent she was busy texting, soon investigators would follow her digital trail to the elusive man who received those messages. coming up. >> we got an ip address that comes back to his residence. >> tracking text messages. >> he said all have an open wi-fi because i run an airbnb business. and so it could be anybody. >> did he run an airbnb business? >> and a tip from a concerned neighbor. >> she described it as just being a really offensively smoky and odorless -- >> when dateline continues. dateline continues forty percent of people with type 2 diabetes will develop chronic kidney disease, or ckd. did you know ckd can lead to kidney failure and dialysis? kidney alert! ckd often has no symptoms until it's too late! help protect your kidneys. call your doctor for a uacr test. it shows one of the earliest signs for ckd. visit kidneyalert.com! i know a thing or two about cars. and, sometimes, buying them can it shows one of the earliest signs for ckd. make you tight in the chest. but with carvana, i can finally breathe easy, buying my car 100% online without any tense negotiation. smells like the internet. shop now at carvana.com. when i'm not racing, i'm personalizing, just like how carvana lets you personalize your financing. you can customize your down payment and monthly payment in a matter of minutes for some truly dazzling results. financing has never felt so fabulous. why hide your skin if dupixent has your moderate-to-severe eczema, or atopic dermatitis under control? 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they found out it had been paid for by a sugar daddy, but remember, mckenzie wasn't on that flight. and they found out she wasn't on the warning to vegas either. >> it was at that point that we were able to say okay, we have enough here that we can build our probable cause back up and really start serving some search warrants again. >> and off the detectives when, in search of the mystery person mckenzie was texting the night she vanished. >> with the 2:06 area code, conversations going well before she left l.a. to all the way where she ended up in hatch park. >> that digital trail eventually led them to a wi-fi router at this salt lake city house, owned by a man for named ayoola ajayi, ex national guard, successful tech worker, part-time model. police knocked on aj's door talked with him and found he was friendly, helpful, sure he said he had girlfriends, but mackenzie they showed him a photo and he -- >> he said he had never seen that lady before. >> so, why than the police asked, did mackenzie get tex routed to aj's wi-fi system? >> he says i have an open wi-fi because i run an airbnb business. and so it could be anything, anybody from here. >> did he run an airbnb business? >> yes he rented out the two bedrooms in his basement for airbnb. >> they looked around, saw nothing amiss and left. and then, that same evening aj stopped by the police station to say that he discovered something. and that he had texted with mckenzie lueck the 92 she disappeared, he had forgotten because mckenzie was the one who reached out to him without identifying herself. maybe, he said, she had seen his seeking arrangement profile. >> so i think that's how she met -- on my profile. >> so she just texted your number? >> yeah. >> he said he had no idea who it was. >> you're still saying that, that's the only text, that's the only messages you got from her, right? >> that i can remember. >> so about, perhaps it just sent me a question mark that i might have talked in the past. >> but she blew him off she said, ghosted him, so he forgot all about it. but he told that story with so much confidence, too much maybe. >> we had two different things, we have an ip address that comes back to his residents and now we know that he had contact with her. >> except, there was no proof mackenzie had been abducted by a.j. or anyone else for that matter, so he was free to leave. but before doing so, he gave the detectives his cell phone number, just in case they needed to get a hold of him. his cell number registered in his name. remember police didn't have that before, they just had that bogus two zero six number used by the texting up. so now, with aj's personal cell number, they could get a search warrant for his calls, and two days later. >> we got the confirmation back from the fbi that mckenzie's record for showing her going from the airport to hatch park and a.g.'s records were showing going from his residence and also meeting up at hatch park at the exact same time. >> and that was enough to get a warrant to search a.g.'s home, where investigators noticed a mattress was missing from the bedroom, and there was a strong smell of bleach. he also spoke with a concerned neighbor, her face blurred in this video. one of the police learned that he had started an illegal backyard fire. >> she described it as being and offensively smoky and motorists. >> debris even flew into the neighbor's yard. >> it looks like there was clothing, pieces of maybe fake a letter, vinyl, we weren't sure what it was. >> what was it like for you when this discovery was made? >> i don't even know how to describe, but it was just a sinking feeling, really, it's like we want to know what happened, but also we don't want to know what happened. because if it is what we think might have happened, we don't want to know what happened. >> coming up. >> that's probably the hardest part in the two instigations is watching him walk out the door that night. >> hard for detectives, but it gave mckenzie's friends reason to hope, -- >> maybe can see was alive and he was hiding her, because the police let him go. >> when dateline continues. hen dateline continues ♪ birds flyin' high, you know how i feel. ♪ ♪ breeze drifting on by you know how i feel. ♪ ♪ it's a new dawn... ♪ if you've been taking copd sitting down, it's time to make a stand. start a new day with trelegy. no once-daily copd medicine has the power to treat copd in as many ways as trelegy. with three medicines in one inhaler, trelegy helps people breathe easier and improves lung function. it also helps prevent future flare-ups. trelegy won't replace a rescue inhaler for sudden breathing problems. tell your doctor if you have a heart condition or high blood pressure before taking it. do not take trelegy more than prescribed. trelegy may increase your risk of thrush, pneumonia, and osteoporosis. call your doctor if worsened breathing, chest pain, mouth or tongue swelling, problems urinating, vision changes, or eye pain occur. take a stand and start a new day with trelegy. ask your doctor about once-daily trelegy. and save at trelegy.com. firefighter maggie gronewald knows how to handle dry weather... ...and dry, cracked skin. new gold bond advanced healing ointment. restore healthy skin, with no sticky feeling. gold bond. champion your skin. >> welcome back, police finally discovered who mckenzie lueck was texting before she went missing, a man who went by a.j., he told detectives they never met in person, but cell phone tracking data place them at the same park and at the same time mackenzie vanished. now investigators were closing in on their suspect, but were there any closer to answering a crucial question, where was mackenzie? here's keith morrison with the conclusion of the waiting car. >> police looking for a mackenzie lueck had heard the disturbing story -- >> i heard -- >> from a neighbor who said that ayoola ajayi had set a suspicious fire. >> the neighborhood found debris in her backyard. so they invoked in a.g.'s backyard, and found something else disturbing, of freshly dug patch of soil. they called in a cadaver dogs, which gave the unmistakable signal, human remains. aj who had been calmly watching it all from his driveway was taken into custody. the team from the crime lab spent the night digging up the backyard. >> they found more burnt closing, and down towards the bottom of the digs site there was a burnt and damaged our phone and, the medical coroner identified human tissue. >> fragments, mind you. they couldn't be certain who or what they had exactly. >> we had these tissue samples or pieces, and so in order to charge somebody or arrest them, that needed to be confirmed and we knew that was going to take time. >> so without solid proof of murder, they once again reluctantly, let aj go. >> it was the hardest part in the investigation, watching him walk out the door that night. >> mckenzie's friends heard he was released and they took it as a sign of hope. >> that maybe can see was still alive and he was hiding her, because the police let him go the next day. >> then at daybreak detectives got a call from the state crime lab about the remains found in the backyard. >> they were able to identify that is being consistent with mckenzie. >> the swat team took a joint custody and police called a press conference to announce his arrest. >> we are finally filing charges of aggravated murder, and homicide of mckenzie lueck. >> kennedy was watching on herself phone. i almost blacked out or something, i dropped my purse, my phone and i dropped to the ground on the street and i was just balling. >> i just couldn't even believe it, i still can't believe it. >> but the detectives work was not done. although they found human tissue in the fire pit, and linked to mckenzie, they had not found her body. so the investigation continued. and, once again, aj's personal cell phone gave him away. >> so that's my phone number -- >> remember when he first spoke to police about mackenzie? well, the very next day his cell phone came its way up into these mountains. >> about two hours north of here, up to logan city and it goes partially up to the canyon and then returns back to salt lake city a couple of hours later. that was odd to us. >> had he exhumed her body from that fire pit to rebury her up here? they set off to search logan cannon. >> they took us a better part of the day until we found her. >> that must be another tough part of your job. >> it was horrific. >> i cited that none of us wanted to see. >> the search for mckenzie was over. but the investigation was not. in the weeks following, a woman came forward to say she had been sexually assaulted by a.j. a year earlier. >> at asians residents, the same residents were mckenzie was killed. >> she said she met him through a dating app a religious one, asia was charged with aggregated kidnapping and forcible sexual abuse in that case. the evidence was tightening around him, evidence of what he did to mckenzie was growing. and finally, october 7th 2020, ayoola ajayi pleaded guilty to murdering mckenzie lueck, and as part of his plea deal he admitted that he thought about killing mackenzie and then planned the killing of mckenzie. a thoroughly pre meditated murder. >> he knew that he was going to murder mackenzie before she even touched down at the airport. >> he selected her as his victim? >> correct. >> was there any explanation at all of what his motivation was to do that? >> none. he never offered any reasoning of why, or even how. >> ayoola ajayi also pleaded guilty to sexually abusing his first victim, he was sentenced to life without parole. oh, one more thing, said the detectives, he was active on the seeking arrangement site right up until he was arrested. >> even after we had made contact with him, he was still on that page, still trying to get a date. >> we don't know why, you know, some selfish and jerk used his position on a dating website to somehow ensnare this bright, pretty woman and for what? >> i mean, you look at his profile pages on these sites and he comes across as a gentleman, somebody who he truly isn't. that's the whole cautionary tale, you never know are they actually who they say they are? >> always she had been surrounded by people who loved her, worried about her, cared about her. mckenzie lueck was an innocent. setting out if only for a moment to explore other possibilities. unaware that in the world she was entering, the innocent can also be pray. >> that's all for this edition of dateline, i'm natalie morales, thank you for watching. >> i'm craig melvin. >> i'm natalie morales. >> this is dateline. >> she is and will always be my sister. i don't know what happened to her. i don't get to say goodbye. it was awful. it makes your whole world follow part. >> if you took her, please just let her come home. >> her name is heather elvis. it was news nationwide when she vanished. >> she had a new job. she was going on a first date. >> it was overwhelmingly horrible.