forth, traumatized, disturbed. >> what the girls seen that day? could they provide a clue to help crack this case? >> we were told by the twins that nikki had a second boyfriend -- >> two boyfriends? >> two boyfriends. >> jealousy, passion, revenge. >> she was fearful. >> she contacted the police. >> what secrets might the twins reveal? >> it's terrifying. is it possible that this could happen? >> i was shaking. oh, my god. oh, my god. you couldn't even imagine. >> i'm lester holt, and this is "dateline." tonight, watch for the double twist. here's keith morrison with "bad blood." once in a while in a complicated life, a woman can get lucky which is why you're looking at the sweet little town called conyers, georgia. antique downtown, ringed by gated communities, good schools, a sheen of newness. it was really pure luck that brought nikki whitehead to this house in this quiet, safe neighborhood. just far enough away from atlanta, that capital of overheated ambition down the highway. here in conyers, she could give her beautiful twin daughters a better life than hers. but of course luck, fortune, can go either way. sometimes in ways very hard to comprehend. >> everything about in goes against nature -- ever being this goes against nature. >> how could indeed do that? >> it was definitely the bloodiest crime scene i've ever been to. >> in the next few minutes, you will know exactly when it happened, where it happened, how it happened. but of course, the real question is why it happened. and the answer to that, as you will see, it's kind of complicated. but that's how nikki whitehead's life was. >> i loved everything about nikki. >> harris grew up with nikki, could see she was a wild child, pretty, fun, and irresistible. >> nikki was, to me, a phenomenal, amazing person. >> yes. and she was effervescent, said nikki's mother, lynda. bigger than life. >> she was the kind of person that when she comes in a room, she just takes over the spe, you know, with her personality, her laughter. >> but when nikki was 12, oh, boy, a handful. lynda was a single mom with other kids at the time, so she agreed to let young nikki move in with della. her grandmother. but della let the girl run wild. boys, parties. >> grew up kind of fast. and then later, she became pregnant at the age -- of 18 or 19. so we moved kind of fast. >> yeah. >> yeah. >> pregnant with identical twins whom she named jasmiya and tasmiya. jazz and tazz. born in 1993. the twins' dad was around briefly, then gone. and their mother figure, nikki's grandmother, della. nikki's mother, lynda, didn't like it. >> i wanted nikki to get her own place, establish her own life, and my mom would discourage that. she would find ways to tell her, no, you're better off here. >> that's how it went for years. but nikki had learned how to style hair and was doing well at it. and eventually saw the possibility of independence. so she eventually wanted to kind of get out from della's control, right? >> definitely, she did. she wanted to -- as the girls got older, she definitely wanted to take control of her life. >> and then one day in 2000, nikki was shopping at the mall. and robert head just happened to be in exactly the right spot. >> i was at the fountain one afternoon about 6:00. and there walked nikki coming into the mall. >> your eye caught dornan. >> -- caught -- >> yes, i couldn't let her go get away. >> that he was old enough to be her father didn't matter. robert was in love. he persuaded her to go to dinner that very night. he took her dancing. bought her nice things. treated her like a lady. >> she was my movie star. that's what i called her, my movie star. >> his movie star with two sweet daughters. he also soon loved as if they were his own. and that's how nikki came here to safe, secure conyers. this is robert's house. here they made a family. unusual some ways as you will hear, but -- >> it was nice. it was really nice. everything clicked just right. >> and she wanted her life to get even better. so while she kept her job as a hairstylist, she enrolled in atlanta's bauder college to study fashion design. >> that's when i actually learned that nikki was a hairstylist. >> rhonda anderson taught a couple of nikki's classes. she thought nikki had a sense of purpose whether it was about her kids, her fashion, or other people's hair. >> i came in to class early one day as i normally. do she looks up and says, "miss anderson, what's going on with your hair?" i said, "what? excuse me?" nikki asked me this question, "do you have a hairstylist? does she know you have your hair looking like that today?" i said, "yes and no." she said, "miss anderson, i'm giving her one more chance. one more chance. if it's not right, i'm taking over." >> rhonda loved nikki, and nikki loved her girls. she put the twins in dance and music classes. at school they won awards. >> their teachers described them as almost angelic, sweet, and happy and engaged. and there's pictures of them, you know, one on each of nikki's arms. >> catie beck is a reporter at nbc affiliate wxia in atlanta. >> teachers describe them that way, that they have a sweet demeanor in their classrooms and with their classmates. they were almost timid. >> and then as they reached their teens, they changed somehow. in the ways children often do, in the way nikki herself once did. and just like nikki, the twins were sent to live for a couple of years with the rather permissive fy della. until 2010 when nikki welcomed tazz and jazz back all together again in robert's house. a fresh start. and nikki turned up at school beaming. >> she was in a very good mood. she looked great. she had a new look with her hair. and she had braids in. and she was happy. >> as if the braids in her hair were kind of an announcement. her girls were back. >> they were pretty much her pride and joy. >> oh, you start thinking about her? >> yeah. hard. it's really hard. >> it was january 13th, 2010. a sheriff's deputy happened to be in the neighborhood. the girls had just come home from school. the deputy saw a look of horror on their faces, heard their screams as they came pounding on his car. >> one of the twins ran up and literally beat on the side of this car and told him that they had come home from school and found their mother murdered. >> murdered in this safe gated community? exactly what had happened? when we come back -- [ crying ] >> they were going in and out of fits of tears and crying. traumatized, disturbed. go two distraught daughters are about to reveal a clue. >> we were told by the twins that nikki had a second boyfriend. >> two boyfriends? >> two boyfriends. military memb, get an auto insurance quote and see why 92% of our members plan to stay for life. 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[ male announcer ] hurry in and spend $399 or more on major appliances, and get a lowe's gift card worth up to $1,000 by mail. ♪ and get a lowe's gift card worth up to $1,000 by mail. say goodbye to the same breakthrough in break time.a introducing the new bacon clubhouse. loosen the tie, punch the clock, and grab 100% beef or premium chicken on an artisan roll with apple wood smoked bacon and big mac special sauce. it's the best thing to happen to lunch since...lunch wednesday afternoon, january 13th, 2010. a gated community in the town of conyers, just east of atlanta. 16-year-old twins jasmiya and tasmiya araved home from school, walked in the front door, followed a bloody trail, and there she was in the bathtub. their mother, 34-year-old nikki whitehead. very, very dead. >> as you walked in -- >> the mess that greeted arriving conyers police detective chris moon told a terrible story. >> this was a long, drawn-out fight. nikki of fighting for her life for several minutes. this was not a quick attack and over with. she fought here. she was struck in the back of the head. she had a laceration to the back of her head. there was blood on the door, on the door handle as if -- >> as if somebody tried to get out -- >> to get out, yeah. then along this wall, you could see a bloody imprint of hair braids which nikki had her hair in braids where she fell, slid down the wall. the most severe blows came when she was facedown in this area. this is clearly where the assailant got on top of her from behind and started stabbing the base of her neck. >> a huge amount of blood here. >> yes. this is the hugest pool of blood in this area here. >> narrator: she was dead or near dead when her assailant dragged her to the bathroom. and that's where she was in a tub of water, what her daughters saw, before they ran to the street screaming. >> as we get there, you have these two beautiful young 16-year-old girls that discovered their mother murdered. >> conyers police captain jackie dunn wanted to get jazz and tazz away gr tfrom the house. that's when he noticed they were hurting themselves. >> one of them of biting their arm. we're like, "hey, why are you biting your arm?" she said, "i'm so upset. i do that when i'm upset." >> this was the worst kind of case. detectives need information fast. how do you get it from childn who have just left their dead mother? [ crying ] >> they were going in and out of fits of tears and crying. >> i want grandma. >> asking for their mom. >> i want my mama. >> they both seemed to be rocking back and forth, you know, incontemplative, traumatized, disturbed. >> i want grandma. >> it will be okay. it will be okay. >> i can remember thinking, man, i hope there is a suitable family member to adopt these girls because they -- they really need somebody to reach out and be good parents for them. >> word spread through the late afternoon gloom. a friend called yucca harris. >> she had asked me when was the last time i talked to nikki. i said, well, i talked to nikki saturday. she had told me that you may want to go over to her house because she said the helicopters were there. and the news reporters. >> tell me when you heard that, what did you think? >> i don't know. it was like tunnel vision. i was just in slow motion. >> yucca called nikki's mother, lynda, told her something bad was going at nikki's. >> i was so nervous, i didn't know what to do. i was like -- oh, my god. oh, my god. i was just shaking. i could hardly drive. >> lynda pulled in to her daughter's neighborhood and saw a police officer. >> said, "ma'am, can you pull over there?" i said, "no. i need to go to my daughter's house." he said, "ma'am, will you just pull over there, please?" i pulled to the side. i said, "what is going on?" he said, "ma'am, the only thing i can tell you is your daughter has expired." >> there is no getting over news like that. as nikki's family tried to take it in, investigators set to work figuring out who did this. the girls said their mother was still in her room with the door locked when they left the house for school at 7:30. >> we missed the bus. so we had to walk. >> perhaps the crime scene would yield more clues than the girls could. lieutenant chris moon headed back there. >> we were looking for cell phones, computers, indications, you know, typically victims are going to have called or spoke weekend their assailant just before the murder or around the time of the murder. >> the attack did not look random. it was not rape, but it was so violent. >> that suggested rage. and when you look at -- at a rage murder, it's usually somebody very, very close to the deceased. >> so naturally the first person they wanted to talk to was the man of the house, robert head, nikki's boyfriend. but robert wasn't around. >> when was the last time you saw robert? >> yesterday. he left -- he came in on sunday. he stayed for a day. he left. >> here's the thing -- robert was a long haul truck driver which explained his absence, but not where he was, especially when nikki was murdered. >> we had to find robert, and we had to check on his gps. >> that takes a while, right? >> yes, sir. writing experience. make it incredibly thin. add an adjustable kickstand, a keyboard, a usb port, and the freedom of touch. and, of course, make it run microsoft office, with the power and speed to do real work. introducing surface pro 3. the tablet that can replace your laptop. t's tackle all this with a splash of style let's go where they know what matters. let's do modest budget major makeover let's do we got this and a whole lotta look what we did then let's sit back and enjoy the view. let's do this. more saving. more doing. that's the power of the home depot. for a limited time shop our newest vanities starting just one hundred eighty nine bucks as parents we hold our kids' hands when crossing the street so think of the internet as the world's busiest street. down somewhere in his brain. >> i haven't made up my mind, but i'm suspicious. coming up -- suspicious? were there reasons to be suspicious? >> we watched the high school video surveillance, and you see the twins showing up about 2.5 hours after they should have for school. >> what were the girls doing the morning of the murder? ♪ if it folds and flips, it's breakfast. if it's fresh brewed, it's breakfast. have breakfast for breakfast. the fresh-made, from our kitchen. the egg white delight. only from mcdonald's. so what are you having for breakfast? ♪ sure science would tell them that these sweet little girls were anything but. did they appear manipulative to you? >> absolutely. i'll give you a for instance. jasmiya is in one room, tasmiya is talken to a smaller interview room. it's apparently that tasmiya knows there's a camera and recording system in the room, and she starts to pray. >> i really want them to catch this person. please, god. >> she knew at some point in time somebody would watch that video, and they would see the young, innocent, sweet girl, asking god to help law enforcement find the person who did this. >> meanwhile, at the glacial pace these things occur, the crime lab worked on the dna and poured over those photos of the bite marks. one on tazz's arm was the impression of a big, ugly bite. they compared the contours of that bite to a mold of nikki's mouth. e jazz and tazz, now 19 years old. and heard them confess they did kill their mother. but was it a confession really? in fact, said the twins, it wasn't their fault. she started it. >> she started cursing and stuff. i think she was mad about us being late. >> that morning they said nikki of furious that they were late for school and picked up a pot in the kitchen, they said, and swung it at them. >> she called us whores and sluts and everything like that and stupid and everything like that. and she -- she threatened us. we all gonna die together. >> that's jazz. then tazz picked up the story. >> you took the pot away from your mom. what happened then? >> she started to charge forward. i didn't -- >> now nikki had a knife said the girls. they tumbled room to room trying to get it away there her before she cut one of the the and i knew -- and they would talk about what college they wanted to go to. i'm sorry. >> it's okay. >> so i'm sitting here, and everybody goes. >> that's an awful tough road. >> you can't even imagine. because every morning i wake up, i think about my daughter and my grandkids. it's just a tragedy. >> one about a mother who dared dream that her sweet gemini twins would surpass her, who instead became their victim. that's all for this edition of "dateline." we'll see you again next friday at 9:00, 8:00 central. up next, something special from our colleague savannah guthrie, new details in a story the whole country was following this very time last year.