something is not right. i just flipped out. i lost it. we could not understand how anybody into -- would want to murder him. >> he looked like he was sleeping except for the bullet hole. >> he was in bed. his head was on the pillow. his entire upper body was tucked in. >> the first guess was suicide. but -- >> there's no gun on the scene. >> hard to have a gun suicide with no gun. >> that's right. >> and this was a man who had everything to live for. >> eric loved life. >> he loved his family and women, too. many women. did one of them love him too much? >> jealousy leads to murder. >> no shortage of lovers to question. >> i knew he was a ladies' man. i'm not stupid.

>> no sign of a break-in either. >> somebody would have to have a key or be let in by eric. >> so it must have been someone he trusted. or maybe someone who didn't trust him. >> inside the safe was a .380 handgun. >> that's the same kind of gun that killed eric. >> same kind of gun. >> everybody loved him. so who killed him? >> we knew in our hearts that this murder was going to be solved. we believed that justice was going to be served for eric. >> i'm lester holt, and this is "dateline." here's josh mankiewicz with "while he was sleeping." he was the life of every party. at 34, eric somuah was charming, magnetic, successful. in 2012, he was living the kind of life that young men liked to brag about to one another. call it the good life, the lush

life, the fast life. it's a world without too many rules. one in which you get close in a hurry. to a lot of people you don't know too well. and it was perfect for eric. living just outside the nation's capital, eric somuah was not only living the american dream, he was selling it, too. the son of immigrants from ghana, eric was a top salesman delivering luxury cars and the fantasies that come with them at this jaguar dealership in bethesda, maryland. >> he was focused and motivated to be the best, and he turned out to be our number one salesperson. >> reporter: this was the guy that could sell ice in alaska. >> right. >> oh, yeah. i tell him, eric, you can sell anything. >> reporter: eric's older sisters, suzie and cynthia, spotted his drive and business savvy at an early age.

>> he started a lawn cutting business in our neighborhood, the neighborhood kids, they were actually working for him. and he would pay them what, $2 to cut the grass. >> reporter: a born capitalist. >> he tell me, suzie, i'm going to be really rich one day. >> he wanted to go all the way to the top. >> reporter: from the day he was born, eric was a charmer and his sisters and big brother michael always adored him. >> just a wonderful, wonderful joy to our family and to my sisters and i. >> reporter: e. >> eric was the baby of the family but we enjoyed him because he was very vibrant. >> it was just the three of us, then he came along. he was sort of our little doll. >> reporter: then eric grew up and became a living doll, to the women of the nation's capital. >> he was a ladies' man, it's no secret. he loved women. >> he walked in a room and everyone liked him, like, oh, who's this guy?

he's so nice, had a beautiful smile. and he'll just start a conversation with anyone. i mean, he just had that type of personality where women liked him. >> reporter: but his sisters hoped their playboy brother would finally settle down. in fact, they were counting on it. >> we were waiting for a huge wedding that my sister and i were planning for him. >> reporter: the bride hadn't been picked out yet. >> no, the bride hadn't -- >> reporter: but the wedding planning was already going. >> the bride had not been picked out yet, but we knew pretty much how the wedding was going to be. >> reporter: eric's sisters admit they knew little about his dating life. his big brother knew much more. >> our relationship was very, very close, even though he's my sibling, my younger brother, he was my best friend as well. we talked about everything. >> reporter: eric's thousand watt charm and his work ethic had earned him success on the job, a high-rise apartment in the d.c. suburbs and a busy and exciting social life.

he was a young man on top of the world. but his big brother still felt the need to occasionally offer advice like that playing the field has its risks and can't last forever. >> he really respected me, the fact that i've been with my wife, we've been together 28 years. he always would communicate and say, hey, i want to be that, but i just can't find the right one. >> reporter: even as the youngest and the only one who hadn't married, eric was the glue that bonded his family. >> eric was the person that kind of brought the family together. he remembered everyone's birthday. he made everyone feel really special. >> reporter: so it wasn't just his customers he was charming. >> no, he was charming his family too. >> reporter: all of you. >> he wanted everyone to come together. >> reporter: in june 2012 he brought them together again, but this time it wasn't for a holiday or birthday. it was because they were worried sick about him. june 5th, a tuesday, eric didn't

show up for work at the jaguar dealership. initially his boss, brian armstrong, led it slide. >> i chalked it up to, hey, he was taking the day off, unscheduled day off, i didn't think too much about it. then the following day, which was a wednesday, again scheduled to come in. no call, no show, then i got worried. >> reporter: word spread and soon eric's sisters and the rest of their close-knit family were trying to find him. >> no one had heard from him. >> reporter: now you're really worried. >> i'm really worried. >> reporter: cynthia took a deep breath and called 911. police were dispatched to check out eric's apartment in silver spring, maryland. his family raced to meet them. eric somuah, a man about town who lived life at full throttle, had seemingly fallen off the map. what had happened to him? >> when we come back, an unanswered knock and lots of questions. >> we were all in shock.

we were just shocked. >> i said there's no way. there's no way. ah! aflac? aflac! i thought you said this guy was the best? oh, he's a horrible stylist. gah? but he's the best at paying claims fast! really... mmhmm. paid mine in just one day. one day? yea. aaaflaaaac! in just one day, we approve and pay. one day pay, only from aflac. (playing harmonica) get your own liquid gold. go on, git! there's gold in them thar shells. liquid gold. i try hard to get a great shape. this... i can do easily. new benefiber healthy shape helps curb cravings. it's a clear, taste-free daily supplement that's clinically proven to help keep me fuller longer.

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it was just alarming when we heard that he hadn't shown up for work. wow. i mean, that's not like eric at all not to show up for work. >> reporter: as his sister cynthia and other family members arrived at eric somuah's building their fear level was off the charts. they stood vigil in the lobby as police went up to eric's sixth floor apartment. what do you think happened? >> i was just trying to figure

out, well, where could he have gone. >> reporter: sister suzy was still on her way when cynthia got her answer from a police captain who had been in eric's apartment. >> when the captain came and gently placed his hand on my arm and said that, ma'am, i'm sorry, it looks like your brother has taken his life. i mean, i was raging with screams. i said, there's no way. there's no way he took his life. eric loved life. >> reporter: through her grief, cynthia managed to call her sister. >> and she was screaming. and she was bawling, and then when she told me eric was dead, i just flipped out. i just lost it. >> reporter: and you show up how long after that? >> we showed up about 40 minutes later. >> reporter: detective dimitry ruvin led the second wave of montgomery county maryland police, after patrol officers made that initial

suicide call. >> they tried not to disturb the scene. so they didn't really look around too much. >> reporter: tell me about the scene. >> he had a gunshot wound to his head. he was in bed. his head was on a pillow. his entire upper body was tucked in. it looked like he was sleeping. >> reporter: detective ruvin and a forensic team continued to work. no sign of a struggle? >> no sign of a struggle anywhere in the apartment. no signs of ransacking. the one thing i noticed right away was there was no gun on the scene. >> reporter: hard to have a gun suicide with no gun. >> that's correct. >> reporter: so this isn't a suicide? >> right. this was a murder. >> reporter: in some ways, dimitry ruvin was like eric somuah. young, successful, driven. but even working homicides, he had none of the world weariness of some veteran detectives. so he was the right cop to break the difficult news to the family. >> i just went downstairs and i said we have reason to believe that eric was murdered. that's when everybody lost it.

i mean, his sister was just crying. his dad had just had his, you know, head buried in his hands and just like -- people just couldn't believe it. >> we were all in shock. we were just shocked. >> who would want to murder eric? >> reporter: that is exactly what detective ruvin wanted to know. >> we started right there. we started our investigation with the family and those that were close to him. just to see if he had any enemies, if there was anybody in his life that would want to hurt him. >> reporter: what's the answer? >> the answer is eric was loved by everybody. and there was no one out there that the family knew that would want to hurt him. >> reporter: eric's head wound, from a .380 caliber gun, indicated to detectives that he was shot at point-blank range. >> it appeared that he was sleeping when it happened. so it would be someone that eric trusted so much that he went to sleep and had that person there. >> reporter: and ruvin quickly learned that his victim, mr. popularity, had welcomed lots of people into his life and into

his home. >> he used to hang out at a local bar just down the street from his house. the owner of the establishment knew him by name. and he would tell us, he would be here every night. and he would go home with a different girl. >> reporter: and his family knew that. they didn't deny that. >> no. >> reporter: it was the kind of thing eric's brother michael had already warned him about. >> could it have been some revenge situation? you know, someone wanted to have him, he didn't want to be with them, and they came in and took him out? we just didn't know. >> reporter: but michael and his sisters did know about one particular girlfriend named denise. >> there were several members of our family who did point to her. >> denise dated eric for a little bit over a year. >> reporter: she's older. >> about 20-some years older. >> reporter: what did you learn about his relationship with denise? >> majority of his family did not like denise. >> reporter: because? >> because they thought she was using eric or she -- they just

didn't like her. >> reporter: detective ruvin's interest in denise intensified when he learned something else. he said denise told him that for a brief time months before the murder she had a key to eric's apartment. they were going out. that seems to make sense. >> right. and there was no evidence of a break-in. so someone either had to have a key or been let in by eric. >> reporter: well, denise certainly would fit the profile of somebody that eric trusted, somebody he'd be willing to go to sleep while they were still there. >> yeah, absolutely. >> reporter: police were eager to interview her. but they knew that, if denise had been in eric's apartment recently, any forensic trail she might have left might not mean much. and the same was true for all those other women police hadn't even identified. >> because the dna belongs there. their dna belongs everywhere in the apartment. their fingerprints belong in the apartment. so now you have to prove it some other way. >> reporter: after day one, ruvin said, denise topped his list of people to check out. but she would not be ruvin's

only lead. >> and the reason is because you're a witness? >> reporter: a witness came forward who'd seen a man meeting with eric, just before the murder. like eric, he was a salesman. but he wasn't selling cars. coming up -- a possible new suspect. >> he's about my color. skinny guy. scruffy beard. >> and a possible motive as old as time. >> jealousy leads to murder. of moderate to severe crohn's disease. and that in clinical studies the majority of patients on humira saw significant symptom relief. and many achieved remission. humira can lower your ability to fight infections, including tuberculosis. serious, sometimes fatal infections and cancers including lymphoma, have happened;

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really here. it was very, very difficult. >> reporter: people tell you grief diminishes over time. but days after eric somuah's death, his close-knit family could only dream about whether that moment would ever arrive. >> when i received the paper the next day and i opened it to the obituary section and i saw this young, handsome guy in there, i just lost it. >> reporter: sadly, i meet a lot of people in your situation. there are families that really want to know what happened, and then there are other people who are like, not going to bring him back and i don't want to spend another minute thinking about the murderer. you guys clearly in that first group. you wanted an answer, didn't you? >> oh, yeah, we wanted to know who would do this because we just could not understand who would want to kill eric. >> reporter: the family had pointed detective dimitry ruvin at eric's girlfriend, denise. >> we interviewed denise multiple times.

>> reporter: ruvin's interest in denise picked up when he learned from the family that her romance with eric was on the rocks. >> he was with her probably about a year. and then after awhile he was just tired of being, i guess, bogged down by someone. >> reporter: according to ruvin, denise told him that she and eric were talking about breaking up by mutual agreement. ruvin said she also acknowledged eric was dissatisfied with their relationship, giving the detective a theory to consider. older woman, younger man. and now, he wants to end it and maybe see somebody else. >> right. >> reporter: and that breeds jealousy and we know what that leads to. >> correct. jealousy leads to murder. >> reporter: while he continued to investigate denise, ruvin learned from residents in eric's building that there was a woman there he'd been dating for just a few weeks. >> that's why we wanted to talk to katrina. >> reporter: katrina ben came

down to police headquarters for an interview. she's visibly upset here. just earlier that day, detective ruvin and his partner had told her that eric was dead. >> i just want to start again by saying just thank you. you don't have to be here. thank you, thank you, thank you for doing this. >> i don't care. oh my god. i want to know, too. >> yes. >> reporter: they wanted whatever leads she could give them. but they began with the basics. >> how did you meet eric? >> i met eric outside, like two weekses after i'd been there. >> reporter: outside their building. >> and he asked me if i was a nurse. because he was starting some kind of agency nursing agency like what i worked for. >> reporter: katrina did work as a nurse for the nih, the national institutes of health. it turned out she and eric had plenty in common. >> i'm a basketball fan and so is he. so that was our connection. >> reporter: the relationship quickly turned more than friendly. katrina said she and eric had

been dating weekly, usually on mondays, ever since. katrina wanted to know about progress in finding her lover's killer. >> we can't really tell you what's going on with the investigation. and the reason is because you're a witness. >> oh, my god! >> reporter: she asked if they could at least say where eric died. >> well, i think we can tell her where it happened. >> he was killed in his apartment. >> reporter: the interview topic returned to the vibrant eric she knew. >> this guy had so many goals and so many dreams. it's just crazy. it's like he was having the best time of his life. and now he's dead. >> reporter: that explained, katrina said, why he never answered her recent texts. >> did he make any calls on tuesday? am i the only -- am i the last person? can you tell me that? i mean, i don't know if he stopped calling me or if he wasn't answering because he was dead? because i've been depressed and

suffering and mad and crying, because i'm thinking he's not talking to me. we've been like this. just to settle my heart, you know? >> i think your heart can be settled. >> reporter: the detectives consoled her but also continued to probe about that last night together. two days before eric's body was discovered. >> i went to his place monday. he stayed with me sunday. >> ok, but monday, you went down to his place to watch the game? >> yes. yeah. >> reporter: but then, she said, the night got strange. out of the blue, eric said he wanted to smoke some pot. >> it's like, hey, whatever floats your boat. >> reporter: but she told him that she wasn't interested. she did agree to ride with eric so he could buy weed at a nearby apartment complex. >> i didn't know what was happening. he's never, ever done anything like that around me. >> reporter: they drove up to this building. almost immediately, katrina said the pot dealer jumped into the back seat. >> and it was real quick. i mean, the light was on, the whole deal, whatever they did. and the guy got out. all this happened before the light could even go out in the

car. because i'm thinking, if you're going to do something like this, turn the light out. somebody might see me. you know, i work at nih. i don't want to be identified in something like this. >> what'd he look like? >> he was bald, and he had a -- he's about my color. skinny guy, scruffy beard. i didn't see his face straight on. i wasn't trying to look at him directly. i'm not trying to look like i want to know who you are. >> reporter: after driving back to their building, eric and katrina spent the rest of the night watching the basketball game before they became focused on each other. >> excuse me, if this is too much information, but we had sex for a while, and i went to sleep. >> reporter: a little later, she told the detectives, she was woken up by the sound of eric talking to someone outside the bedroom through a crack in the door. katrina thought she could make out a face. and the man looked familiar. >> she believed the guy to be the drug dealer. >> reporter: the same guy she'd met earlier? >> yes. >> reporter: this was only hours before eric was murdered in his bed. detective ruvin now had another

major suspect. >> so we concentrated on the drug dealer. >> reporter: this would prove to be a critical moment in the case, but not for the reasons you think. coming up -- police strike gold maybe in the drug dealer's apartment. >> same kind of gun. >> but struck out with katrina. >> she flat-out refused to give us her phone. >> why? does your makeup remover take it all off? every kiss-proof

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worked a lot of homicides. but the death of eric somuah angered him more than most. >> you know, he was just sleeping. to kill somebody while they're sleeping is just -- it's horrible. >> reporter: eric's sisters were grateful to have someone as committed as ruvin working their brother's case. >> he is a phenomenal investigator. >> reporter: and now just days

after eric was murdered, it looked as if detective ruvin might give the family some resolution. one of eric's lovers, katrina ben, handed the investigators a new suspect, eric's pot dealer. >> it didn't make sense to me. because i was thinking, why is he here? >> reporter: katrina told them how uneasy she felt with the dealer in the apartment. >> it was just a little uncomfortable. he just seemed a little weird. >> reporter: so at just around 5:00 a.m., katrina said she got out of there. >> she said the guy then just came up to her as she was leaving and basically pushed her out with the door. >> reporter: based on katrina's account, the police believed eric was killed sometime in the early morning hours of june 5th. ruvin brought in the dealer for questioning, a man named william woodfork. >> and he was like, i have no idea who that is. never met him before. >> reporter: did you believe him? >> no. i knew eric called him. and katrina's story tied him to eric.

>> reporter: ruvin hammered away at woodfork for hours finally getting him to admit he sold eric marijuana the night of the murder. but the dealer balked when ruvin asked why he later went over to eric's. >> and he was like, what are you talking about? he was so adamant about not even knowing where eric lives. you know, "i'm a weed dealer. i'm not a deliveryman. i don't deliver. people come to me." >> reporter: detective ruvin wasn't about to just take a drug dealer at his word. >> so we end up getting a search warrant for his place. and be recovered a safe from his apartment. and inside the safe was a .380 handgun. it was just like, did he lie? is this our murder weapon? >> reporter: that's the same kind of gun that killed eric. >> it's the same kind of gun. >> reporter: the gun was sent to the firearms lab as ruvin checked to see if he could prove william woodfork was in eric's apartment. but woodfork's dna and fingerprints weren't on the

door or anywhere else. you look at the security tape? is he on there anywhere? >> he was never on the security tapes. >> reporter: then the tests came back on the dealer's .380. >> it was not the gun that killed eric. it was the same caliber, but the ammunition was different. so it was just one big coincidence. >> reporter: now eric's dealer wasn't looking as good for the murder. not only was the gun not a match, ruvin was convinced that the dealer was never at eric's apartment. as for denise, the woman who had been eric's girlfriend, investigators interviewed her three times. she was cooperative and allowed them to look at her phone. >> her phone records put her at home the night of the murder. >> reporter: so they eliminated denise as a suspect. and again, ruvin started from scratch. >> you don't just come in to somebody's apartment and murder them while they're sleeping and expect to get away with it. and i felt like this was my job to find the killer. and i felt like i wasn't doing my job. >> reporter: the detective

circled back to the person who pointed them towards the pot dealer in the first place -- katrina ben. the woman who'd been so surprised and distraught by her lover's death. now the cops wondered if she had deliberately misdirected them. ruvin and his partner asked her back for another chat. >> did you think he was the one? >> eric? did i think he was the one for me? actually, no. but he was trying to convince me that he was the one. >> reporter: just days before katrina had spoken of eric lovingly, but no longer. >> i knew he was a ladies' man. i'm not stupid. >> at some point i asked her to give us her phone because i knew she exchanged messages. and she just flat-out refused to give us her phone. >> reporter: well, that has to make you sort of sit up and take notice. >> yeah, it was a little odd. but at the same time if it was somebody -- my significant other

that was murdered, i think i would do anything to help the police. >> reporter: and she wouldn't do it? >> no. >> reporter: katrina's abrupt change in behavior was strange, even alarming, to the detectives. but all they could do was say their good-byes as katrina headed off to a new job in baltimore. >> at this point there was enough weird behavior from katrina ben. we had nothing solid. nothing really incriminating, but it was just something not being right there. >> reporter: the cops had a nagging feeling katrina ben was lying. that pot dealer wasn't in the apartment the night eric was murdered, but katrina was and suddenly she looked suspicious. but suspicions don't make a case. and right now someone was getting away with murder. coming up -- a damaged gun helps a determined detective shoot a bull's-eye. >> it was recovered the day

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as his murder investigation slowly rolled forward, detective dimitry ruvin developed a certain affection for eric somuah, the guy he'd never met. the successful, charismatic, charming victim. you kept a picture of eric on your desk at work? >> mm-hmm. >> reporter: just to remind you? >> we called him the most interesting man in the world. that was the name of the case. and i've always had a picture of eric to kind of remind me to keep going, keep working the case. >> reporter: unfortunately, what wasn't next to eric's photo on ruvin's desk was any hard evidence against katrina ben, the woman ruvin thought knew more than she was telling about eric's murder. he decided to take yet another crack at his suspect, and along with another detective, ruvin paid katrina a visit up in baltimore. >> for the most part, her story

remained the same. >> reporter: but katrina was also on guard and defensive. >> don't go there with me. >> don't go where? >> no, i feel like you're trying to be sarcastic. >> reporter: instead of focusing on the detectives' tone, katrina should have paid more attention to their clothing. the detective secretly had a tape recorder in his pocket. >> and that's when i asked her about owning any guns. did you own a gun? >> no. >> have you ever fired a gun? >> no! >> reporter: armed with a warrant, ruvin searched katrina's apartment but did not find a gun. he seized her phone and computer, but cops didn't find anything incriminating. there was no gun registered to her anywhere? >> no. >> reporter: and no sign that she'd ever owned one at any point in her life. >> that's correct. >> reporter: ruvin kept going. >> i subpoenaed her bank records and credit card records. just to see if she purchased any ammunition somewhere. >> reporter: but you didn't find it? >> no. >> reporter: ruvin didn't stop there. he kept looking everywhere.

he even went all the way to katrina's home town in mississippi, where he learned something interesting. >> i talked to her dad, who said that he had guns, multiple guns in the house and that katrina had shotguns before. so we knew she lied. >> reporter: but that is no criminal offense. still, ruvin was certain he could eventually find something concrete, and he kept looking. weeks passed. then months. >> i think that's probably the toughest thing about this job is if it goes unsolved for a while -- >> reporter: you feel like you're letting the family down. >> right, exactly. and especially families that do stay in contact with you. >> reporter: eric's family was eager for answers. they were not shy about letting ruvin know that. >> he gets probably daily phone calls from each one of us, and he was so patient in just explaining -- >> reporter: detective ruvin never said to you, hey, maybe like one of you could call me

and tell the other people? >> no. >> never. >> and you look at your phone and you're like, you don't even want to answer them because you have no news. it's the same that it was last week. we think we know who did it, but we can't prove it right now. >> reporter: may 2013. the one-year anniversary of eric's murder approached. and frankly, the investigation had come to a standstill. ruvin wasn't just angry. he was frustrated. he needed to make something happen. ruvin thought about the gun that had killed eric, and he knew a lot of handguns just like it were already in police custody all across the d.c. area. he decided to examine all of them. it was an immense task. he began in montgomery county. >> so i decided to look at all .380s which had been recovered in the past year. >> reporter: which was about how many? >> it was about 60 guns. >> reporter: ruvin combed through the records for each of those guns, most seized by cops in traffic stops or drug busts,

but none matched up. until ruvin read the second to last file. it was handgun number 59 out of 60. it was a gun turned in by a tourist from montana who had spotted it lying by the side of the beltway, d.c.'s most traveled road. the only reason the man saw it was because he was parked in d.c.'s famous bumper to bumper traffic. >> it was recovered the day after we found eric's body. it was a short distance away from the crime scene. and i was like, let's just test this gun. this gun makes sense. >> reporter: this seems like succeeding against unbelievable odds. >> one in a million. >> reporter: the gun was a mess, missing most of its components, and it looked as it might have been run over after it hit the pavement. but the barrel -- intact. using spare parts, the police firearms lab reassembled the weapon and test-fired it.

the result -- a close match to the bullet that killed eric somuah. and on the gun, a serial number. from it, ruvin learned something else. where was it originally sold? >> it was sold at a pawn shop in columbia, mississippi. >> reporter: why was that a big deal? because that little pawn shop was just a few miles down the road from silver creek, mississippi, which was the hometown of katrina ben. ruvin just couldn't buy that as a coincidence. so he took another trip down to mississippi. this time to track down the gun's original owner, which was harder than it might sound. >> this gun had multiple, multiple owners. it would take me 30 minutes just to persuade somebody to talk to me. >> reporter: why? because in mississippi you sound like a stranger? that's so weird. >> possibly sound like a stranger. also, nobody wants to talk about guns. they always think that i'm there to get them in trouble.

>> reporter: it was a lot of shoe leather, and ruvin still didn't have a solid ling to katrina. >> it would take some persuading from me to even have people talk to me. >> reporter: but slowly the persuasion paid off. >> and each would tell us, yeah, i had it for a year. and then i pawned it at this pawn shop. >> reporter: after interviewing six former owners of the gun, ruvin arrived at a pawn shop that bought and sold it sometime around 2003. >> so the owner, he was like, we keep our records in diaper boxes in the back of the shed. and the rats were eating on them. so we decided to just send them to the atf. >> reporter: ruvin offered to come look through those diaper boxes. the response from the atf? thanks, but no thanks. >> the atf agent was just saying, just let us take care of it. so we left mississippi really with nothing. >> reporter: ruvin returned to maryland, wondering if he'd hit another dead-end. he wondered for about a week.

it was late june, now more than a year since eric was murdered, when an atf agent called back. >> we found these diaper boxes. we found these records, and we're faxing a receipt. so i was waiting by the fax machine. the fax came through. i looked at the name, and it was katrina ben. she was the last purchaser of that handgun. >> reporter: and you've got her. >> oh, yeah. it was pretty incredible. i was literally jumping up and down. >> reporter: now he just had to lasso katrina ben. easy? you decide. >> and if i was going to do something like this, it would be -- it wouldn't be like this. it wouldn't be stupid. coming up -- was katrina ben a monday night girl? >> a girl who you do not take out, you do not show off and you do not introduce to your friends. she had her purposes. >> and was that a motive for murder?

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eric somuah had

been dead for more than a year, and still no one had been arrested for his murder. but his family, bound together by grief and faith, felt a kind of serenity. >> i believe that there were certain people that were destined or ordained, i would say, to work this case. detective ruvin, outside of his normal business hours, was very determined. and he persevered beyond what a normal detective would do. >> reporter: the family didn't know it yet, but that perseverance was about to be rewarded. detective ruvin had an arrest warrant for katrina ben. she was living back in mississippi, which is where the cuffs went on to her wrists. >> you have the right now and at any time to remain silent. >> reporter: but katrina ben did not remain silent. not at all. >> and if i was going to do something like this, it would be -- it wouldn't be like this. it wouldn't be stupid, you

know. >> how would it be? >> i think it would be planned out. >> reporter: ruvin had dropped the friendly facade he'd once presented to katrina. now he came at her full force. >> so you're still saying you didn't kill eric? >> of course not. >> okay. did you -- do you own a firearm? >> yes. >> okay, what kind of firearm do you own? >> a .380. >> reporter: remember, katrina had told police she didn't own a gun, hadn't even fired one. >> why didn't you tell us that last time? >> because you never asked if -- i didn't kill anyone, so there's no need for me to say i have a gun. i mean, you never asked. you asked me, have you ever held a gun. have you ever fired a gun. >> reporter: it was simple, they told her. she murdered eric. >> it was your gun that killed him. that's a scientific fact. >> reporter: the question was why. >> there has to be a reason. there has to be a reason. and if there isn't a reason,

then you're going to go down, i'm telling you, as the most cold-blooded person that we've spoken with because you're so good. it's going to look horrible. it's going to be bad. >> i'm just going to have my day in court. >> i'm telling you -- >> reporter: but katrina wouldn't give it up and asked for a lawyer. the detectives put her in lockup and ruvin stepped outside to call eric's family. >> i was just like, you know, thank you, god. they're going to get this woman. >> reporter: getting a conviction was ultimately the responsibility of montgomery county state's attorney john mccarthy. even with gun, which gets you an arrest and into a courtroom, this was pretty far from an ideal case. >> absolutely. to sell this to a jury when you are basically saying that she felt so betrayed after a three-week relationship that she was driven to murder, that's a little bit of a tough sell. >> reporter: mccarthy assigned the case to assistant state's attorney jessica zarrella. at trial last october she gave

katrina a nickname that few would envy. why did you refer to katrina as the monday night girl? >> it was used in the context of a girl who you do not take out, you do not show off and you do not introduce to your friends. she has her purposes, but those purposes are relegated to monday nights and not the more high-profile saturday and friday nights. >> reporter: this was the prosecution theory. katrina learned, maybe from eric's phone, that she was far from the only woman in eric's life. jealousy and anger did the rest, and katrina shot eric while he slept. >> human emotion fuels most homicides. >> reporter: what i keep thinking of is sort of "fatal attraction." an insignificant relationship on one side and a very significant relationship you ask the other person. >> obviously, he made a misjudgment when he became intimately involved with her. and the sense of betrayal that she felt is what fueled this homicide. >> reporter: and, said

prosecutors, after katrina killed eric, she quickly ditched the gun and began playing the part of the concerned lover. but she couldn't keep her story straight. >> lies upon lies upon lies to bury the truth and that ultimate truth in this case was that gun. >> reporter: the crux of katrina's defense was that she had no reason to kill eric because she just wasn't that into him. >> eric was a great guy, but i wasn't even trying to be with eric like that and, to be honest, he would tell me he was in love with me, i never believed him. >> reporter: what's wrong with the argument that, you know, this was a woman who discovered there were other women in his life and she got incredibly jealous and angry and that tipped her over and she killed him. >> it just doesn't work for ms. ben. >> reporter: karl-henri gauvin was one of katrina's lawyers. >> we have to look at the timing in which these two parties were intimate with one another, a matter of weeks. and so to say that the

relationship was at such a strong level that she would become jealous or irate to the point where she would murder somebody doesn't resonate with the time in which they were together. >> reporter: as for that gun, katrina's attorneys argued that the traveling nurse had long since lost track of it. they said someone could have stolen the gun along the way and used it on eric. >> reporter: she shifts from one residence to another from state to state because of her profession. she may have left the gun -- she was unaware, rather, of where the gun may have been. >> reporter: jurors were not swayed. it took them just six hours to find katrina guilty of murder in the first degree. >> there's no doubt in my mind that had she not been convicted of this crime, katrina ben was just as likely to encounter someone else who disrespected her in the same way that she felt eric did and -- >> reporter: with the same result. >> visit that ultimate consequence which is take his life. >> reporter: the real jaw

dropper came at sentencing when katrina addressed the courtroom. >> she stood up as if she was giving a eulogy of my brother. telling us i'm sorry for your loss and all this stuff. it was like a slap in the face. >> she was talking about the murders as though she wasn't even there. you killed this person. you're the reason why we're here. it was just unbelievable. >> reporter: the judge sentenced katrina ben to life plus 20 years. >> justice has been served today, and what you have sown into the life of our dear brother, cousin, nephew, friend, you will reap bountifully with life in prison. >> reporter: now three years after saying goodbye to eric, his large loving family still feels the pain of that loss. >> we do remember eric every day. all the good times we had. it's unfortunate that we have to think about the day that he was brought home from the hospital

to the day that we actually closed the casket. >> reporter: what they want to do is warn other families to watch out for the other katrina bens in the world. >> i pray and continue to pray that, even in doing this, that it will bring awareness to other people out there about certain types of people and just being very cautious and being aware. >> reporter: so the lesson is be careful who you get close to? >> be very careful. very aware. very important. >> that's all for this edition of "dateline." we'll see you again sunday at 7:00, 6:00 central. i'm lester holt. for all of us at nbc news, good

right now at 11:00, three big stories. celebrating into the night after same-sex marriage becomes the law of the land.