assassination. >> nick, the marine, a tough vet-turned-target. >> somebody hated nick so much that they shot through his window. >> then came in through the window and shot him some more. >> yes. >> angry colleagues at work. >> people complained of how nick talked to them. >> which was, let's go. >> get the job done. >> and some angry exes too. >> i know he was cheating on me. >> he's dated a number of women. >> maybe he made the wrong one angry? >> that's what we thought. >> bullet casings, carpet fibers, bloody clothes. who was the killer? >> it's somebody full of hatred. >> we wanted answers. >> there needs to be justice. >> people are no good at getting away with murder. ♪♪ >> hello and welcome to "dateline." kristy said she waited 40 years for nick morelos to come into her life. the happy couple were engaged to be married when suddenly her world crumbled. she found nick gunned down in his own home. detectives went through a pool of suspects, from spurned lovers to office enemies before a boost from nick's brother helped reveal the true killer. here is josh mankiewicz with "stone-cold." >> reporter: put people together in a workplace and things can develop. friendships, rivalries, sometimes even love. most of the time it's not a problem. but in this case, it was deadly. >> 911. do you have an emergency? >> he's just laying there, and he has a bullet hole in his head. >> this is a stone-cold assassination. >> it was like our house was turned into a shooting gallery. >> reporter: one man's militant style of doing business that left a trail of bruised egos in his professional life. >> if you're not doing what your job requires, he's going to let you have it. >> reporter: and a trail of broken hearts in his personal life. >> at work i could tell that he was probably a pretty good womanizer. >> reporter: by the end of it, investigators would discover a world of grudges and a hotbed of affairs and messy love triangles. and it all began with this man, nicolas morelos. >> we were constantly teasing and messing with each other. >> reporter: john morelos and his brother nick grew up outside tucson, arizona. what was he like as a little brother? >> a prankster. he was either going to get in trouble or he had already done something that would've gotten him in trouble. >> or he was going to get you in trouble. >> absolutely. >> reporter: just 18 months apart, john and nick were close, partners in crime, brothers who had each other's backs. and just like his brother, nick served in the military. at 18 he enlisted in the marines. in 1990, he fought in operation desert storm. >> he came back a changed person, very motivated, very dedicated. >> maybe he was a little less of a jokester and a little more of a straight arrow? >> very much so. definitely more -- more serious. >> reporter: after the war, nick returned to tucson and settled down. he married and had a son, nicolas jr. and while nick loved being a father, the marriage didn't last. >> it really hurt him for many years. he told me that he would never get married again. >> reporter: actually he did, but that marriage didn't work out either, and nick focused on work. starting as an aircraft mechanic, he quickly rose to director of maintenance at what was then marana aerospace. >> that's the fastest i've seen anybody move up through the ranks. >> reporter: bob welsh was a client who brought aircraft to marana for service. >> he was not a, per se, people person. >> reporter: within the walls of marana aerospace, nick was tougher than an irs audit and every bit as unforgiving. but at the same time, he wasn't devious or sneaky. nick morelos would stab you in the front. >> he didn't know how to approach people and just have a conversation about, hey, maybe you should do it this way rather than this way. >> it was, you're doing it wrong. start doing it right. >> and if you don't do it this way, go home. >> reporter: john, a lieutenant colonel in the army, worked at the same air park as nick. what would people say about him? >> he was -- he was tough. he was, excuse the language, a hard ass. very vocal, intimidating to some. >> reporter: there was one area where nick seemed quite popular -- with women. and conveniently marana aerospace employed some. do you have any idea how many women at marana he dated, how many of his co-workers? >> he only admitted to me two. there was a lot of rumors, but he told me of two. >> reporter: and one of them changed everything. in 2016, nick met kristy. >> i liked that he was such a hard worker, and he was so smart. >> reporter: no immediate fireworks, but as kristy and nick got to know each other, they realized they both loved books, dogs, and plants. >> he was the tough guy at work, and here he is, you know, tending to these delicate plants and talked about how much he loved his dog. >> reporter: his dog smokey, an american pit bull terrier. >> to look at smokey, you would think, oh, my goodness, there's this big, scary dog. and this is the most gentle dog you'll ever know in your life. >> reporter: kristy fell not just for smokey but for nick too, and hard. you sound kind of swept off your feet. >> i was. absolutely. never -- never knew a man like that in my life. he was -- he was my superman. he was always my protector. >> you could see it in his eyes. he was happy. his heart was full. he spoke to my parents about things that we'd never thought he'd talk about. >> like what? >> a marriage. >> serial monogamist. >> yes. >> finally settling down. >> yes. >> reporter: before that, nick and kristy came to an agreement, that the past was the past. he dated a lot of women in that same company, some of your co-workers. that give you any pause at all? >> oh, absolutely. you know, my outlook was, look, we both have a history, you know. you're single. he's allowed to date who he wanted to. >> reporter: nick and kristy got engaged. by july 2016, they were making plans to move in together. >> he just looks right at me, and he just said, i just want you to know how much i love you and appreciate everything you do for me. i just remember walking in the kitchen and thinking, god, i am so lucky. i am so lucky. >> reporter: 24 hours after that moment came this call. >> my fiance, i think he's been killed. i think he's been shot. >> coming up, what had happened to nick? >> i zeroed in on him, and he was just laying there. >> curious clues in the garage. >> immediately i noticed a bucket full of water and some carpet fibers. >> and blood in the bedroom. >> the floor was very sticky, and it smelled very heavily of mouthwash. we felt that whoever did this tried to clean up whatever tracks they left. >> this is the man i'm supposed to marry. this was just not -- not possible. >> when "dateline" continues. there's an invisible threat in your backyard that could cause deadly heartworm disease for your dog. but not if you protect him every month with heartgard plus, the #1 choice of dogs. digestive and neurological side effects have rarely been reported. ask your vet for heartgard plus. i'll be observing your safe-driving abilities. play your cards right, and you could be in for a tasty discount. [ clicks pen] let's roll. hey, check it out. one time i tripped on the sidewalk over here. [ heavy-metal music playing ] -[ snoring ] -and a high of 89 degrees. [ electronic music playing ] ooh! ooh! who just gives away wood? the snapshot app from progressive rewards you for driving safe and driving less. there's an app? -[ chuckles ] beth. -save money with progressive. [ tires screech ] well, that came out of nowhere. what is humana doing sending me a diy test kit? old health insurance reminds you to schedule a screening, say, for colon cancer. humana does you one better and sends you an at-home test kit, when it's overdue. huh! one of those tests could save your life, or at least a little hassle. or both. yeah! you get it, you do it, you send it back. i get it, i do it, i send it back. you get it, you do it, you send it back. yeah, i got it. you got it! ♪ ♪ humana. a more human way to healthcare. i just felt like i can't believe i get to be his bride. i was just -- i was excited. i waited 40 years for him. >> reporter: kristy and nick were engaged to be married. >> every morning started with either a text or a call. good morning, i love you. have a great day. every night, same thing. >> reporter: so when kristy awoke monday, july 18th, 2016, and saw that nick, an early riser, had not called, she was immediately concerned. >> of course i'm rationalizing. oh, maybe he got stuck on a call with his boss, or maybe he slept in a little bit, you know. >> reporter: a few hours later, still no word from nick. so kristy drove to nick's house and went up the stairs to the master bedroom. the door was barely open. >> i zeroed in on him. he was just laying there, and he was just -- just full of bullet holes. >> he's just laying there, and he looks like he has a bullet hole in his head. >> this is the man i'm supposed to marry. this was just not -- not possible. and the police arrived, and the nightmare began. >> we received a message advising that there was a homicide on the north side and that the whole unit needed to respond. >> reporter: pima county sheriff's detective jennifer garcia had been in the homicide unit for all of seven months. this was a call she'd prepared for ever since she was a little girl and saw her grandfather in uniform. >> it was just something that i've always wanted to do, you know, sort of my dream job. >> reporter: and now here she was, lead detective in the biggest murder investigation in tucson. she began by methodically walking through the scene, nick's house, starting in the garage. >> immediately i noticed a bucket full of water and some carpet fibers, which at the time i thought was odd. >> reporter: inside the cabinet under the kitchen sink was open. in the living room, cleaning products left out. and in the backyard was a large pit bull. presumably whoever lived there had let the dog out? >> possibly, yes. >> or the killer had. >> yes. >> reporter: as detective garcia went up the stairs, she saw bullet holes in the wall. at the top, the master bedroom door was ajar. >> i immediately saw a bloody foot of nick morelos. i opened the door and saw his naked body laying there riddled with bullets. >> reporter: a lot of people will tell you that when their time comes, they want to die at home. very few will say they want to go the way nick morelos did, in his bedroom, alone with his killer, in a hail of bullets. nick had been shot eight times, including once in the middle of his forehead. >> they shot through his window and assassinated him. >> then came in through the window and shot him some more? >> yes, until he was finally dead. >> reporter: detective garcia believed the killer climbed onto the roof outside nick's bedroom. that's where she found blood on broken panes of glass and on the stucco. so maybe the killer cut him or herself coming in through that window? >> yes. >> reporter: there was blood throughout nick's bedroom, in his closet, and on a mouthwash cap in his bathroom. >> the floor was very sticky, and it smelled very heavily of mouthwash. so we felt at the time that whoever did this tried to clean up whatever tracks they left. >> reporter: in the bedroom, more evidence the killer tried to clean up. >> it appeared that the rug under the bed was cut. like half of the rug was gone. >> reporter: detective garcia believed the killer bled so heavily on the rug that he or she cut the rug and took it right out of nick's house. there was also evidence the killer failed to get rid of. garcia's team recovered 11 shell casings, each with a unique five-star stamp. and this was odd. 11 shots, yet none of the neighbors called 911. >> very early on, the detectives that i was working with, who have done previous homicides, they believe that a silencer was used. >> reporter: one neighbor said she heard a noise around 4:00 a.m. but wasn't sure what it was. investigators thought that could well be nick's time of death. while detective garcia worked the scene, two other detectives went to john morelos' office to tell him what had happened. then john had to break the news to his mother. a tough conversation to have. >> oh, most definitely. that was probably one of the toughest things i've ever done in my life. >> reporter: kristy also wrestled with her new reality, a life without nick. >> i went from this amazing life to just, you know, being traumatized and just complete disbelief. >> reporter: while nick's family faced the loss of a man they loved, investigators began to learn what nick's co-workers and exes already knew. he was not beloved by everyone, not by a long shot. >> coming up, angry colleagues on the job. >> people complained of how nick talked to them. >> except the way nick talked to them was kind of what nick was being paid for. >> correct. >> which was, let's go. >> were any angry enough to kill? >> feels to me like maybe there are a lot of people you might want to be talking to at the office. >> yes. the list was very long. >> when "dateline" continues. s l natural fragrances, inspiring air wick to create our new spring collection. so we're partnering with world wildlife fund to reseed native wildflowers and grasslands. learn more at airwick.us (man) 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. (deborah vo) i was hesitant to get the hearing aids because of my short hair, but nobody even sees them. (vo) discover the exclusive, new miracle-earmini- a nearly invisible hearing aid from the brand leader in hearing aids with over 70 years of experience. (deborah) when i finally had miracle-ear and i could hear for the first time, i started crying. i could hear everything. new miracle-earmini. so small and comfortable that no one will see them, but you'll notice the difference. call today to start your 30-day risk-free trial at your local miracle-ear. ♪♪ >> reporter: often at "dateline" we tell you the stories of murder victims who lit up the room or who didn't have an enemy in the world. well, not so much with nick morelos. he definitely knew how to light up a room, but depending on which room it was, there might have been people in it who actively wished him ill. that was true in his personal life, and it was true here at work. the question for investigators, which side of nick's life had caught up with him? detective garcia quickly began to find out how much nick's leatherneck exterior had rubbed people the wrong way. jeff johnson was h.r. director at marana aerospace. >> i did have some exit interviews that people complained of how nick talked to them. >> except the way nick talked to them was kind of what nick was being paid for. >> correct. >> which was, let's go. >> get the job done and get it done on time and on budget. >> he was brought in to sort of be the hammer. >> exactly right. >> reporter: but when you're hired to be a hammer, sometimes everything and everyone starts looking like a nail. feels to me like maybe there are a lot of people you might want to be talking to at the office. >> yes. the list was very long. >> reporter: a lot of them had petty grievances, like a safety inspector named james lapan. >> it's just we never got along is the thing. >> reporter: lapan told investigators nick had given him a hard time for parking his car in a restricted area and had accused him of using a personal tablet computer during working hours. >> anybody you know that wants to kick his ass? >> kick his ass? no. >> reporter: maybe not over a parking spot, but then detective garcia started learning for herself about the other part of nick's life. this was a guy who made a lot of women angry. >> yes. >> reporter: his second ex-wife once threatened to kill him. an ex-girlfriend slipped into his house, and nick woke up to find her watching him and a new girlfriend while they slept. and then there were nick's romantic entanglements at work. >> we did not have a fraternization policy. >> and nick, i think, took advantage of that. >> i think so, from what i heard. anytime i questioned nick on it, he would deny it to me, for good reason, i'm sure. >> because you were the h.r. director, i'm thinking that might be the reason. >> correct. >> reporter: long before nick met kristy, he was involved in a relationship that now caught detective garcia's attention. >> he was a really, really, really hard worker. >> reporter: claudia banks worked in administration at marana aerospace. she and nick dated for six months. >> he was awesome. he really was. >> reporter: claudia told detective garcia she'd had a good relationship with nick. however, that came at the expense of someone else, her ex-boyfriend, justin skinner. claudia moved in with nick and broke up with justin almost in the same breath. >> yes, that's right. >> reporter: claudia told detective garcia she tried to cut off all contact with justin. >> and shortly after the breakup, it was reported that he had followed claudia while she was driving her vehicle, and nick was in the vehicle. >> reporter: claudia also said justin unexpectedly came by her home a couple of times. then the day nick's body was discovered, claudia said she went out with her mom. >> me and her went to circle s. >> reporter: the circle s saloon, the proverbial bar on the outskirts of town, where she saw justin. >> did he have any marks on him at all? >> i saw him and pretty much walked -- just walked right by. >> reporter: the next day claudia said justin left a note on her front gate about her ex-boyfriend, nick. >> saying, hey, i heard what happened, and i'm really sorry. if you need anything, let me know. >> reporter: and claudia directed detective garcia's attention to yet another ex-girlfriend from nick's past. >> before me, he was dating a girl, um, jessica. i don't know if you've spoken to her yet. >> reporter: jessica stillwell, another of nick's girlfriends from marana aerospace. she and nick dated for about six months, even lived together for a while. >> she seemed nice. never saw them argue. they always seemed happy and giggling together. >> reporter: detective garcia learned that didn't last. nick abruptly kicked jessica out of his house and his life and moved claudia into both. and then garcia heard about something that happened shortly after claudia and nick started dating. >> claudia was at his house, and jessica showed up, seeing her vehicle in the driveway area and was very upset, banging on the door, saying, i know she's in there. let me in. >> reporter: nick had told his brother, john, about the dustup with jessica. and he thought that was, what, amusing, alarming? >> he's like, man, it's going to be drama. i can already tell. >> reporter: and then a day after nick's murder, john's kids snapped these pictures of a woman poking around nick's house. >> my children were adamant that it was jessica. >> does it seem at all significant to you that nick was murdered like almost exactly a year from the time of his breakup with jessica. >> i found it very odd. >> or very coincidental. >> correct. >> reporter: the number of scorned lovers in nick's past was enough to warrant a scorecard, and investigators weren't even done counting. there were more answers to be discovered in the place where so much of nick's social life was centered, marana aerospace. >> that mystery woman at nick's house, was it an angry ex? coming up -- >> some of the family identifies you as being the one that wa