>> she is the definition of grit. >> she didn't give up. >> he's hurting me. >> the details that she gave. >> it was unbelievable. >> she said, you did it. i said, no, you did. route 66 once stretched across the southwest from one horizon to the next, going from what america was to what it wanted to be. cities like albuquerque, new mexico, were celebrated stops along the journey. today buildings that once lined this part of the iconic highway faded and closed as the cotton wood mall became the new downtown. >> the mall was the big hangout. >> i met my husband at the mall. >> so did i. >> it has played a pivotal part in our lives. >> for the marcell sisters, all six of them, along with their brother, jonathan, the cotton wood mall in albuquerque was important in their lives. 17-year-old brittani worked at a sunglasses kiosk. >> she is this blue-eyed girl with a big eyes and a striking mile. >> everything was good, until september 11th, 2008, brittani just starting high school had planned to meet her mom for lunch. >> i saw her favorite pair of sunglasses on the floor, and i thought that was weird. >> a seemingly trivial detail now burned into her memory because of what came next. >> i see her lying on the floor, and bleeding profusely. >> then what do you see. >> i see a person i never have seen before in my house, and he is holding a shovel, and he works through the living room and drops the shovel and around to the kitchen, and i am looking at him and he tells me i am next while he's reaching for a butcher knife. >> he's going to kill you? >> yes. >> what do you do? >> i ran out. i'm screaming and yelling. >> diane's screams got the attention of a passerby who was brave enough to help. >> he yelled back, you better get the paramedics here, she's going to die. >> diane waited outside, certain the attacker was still in her house. >> i am afraid to walk in, and he was coming after me, he ran to the kitchen. >> police and paramedics were there in minutes, and brittani was taken to the hospital. >> i thought she was in a car accident and we didn't realize what happened. >> i rushed home to my mom and she told me what happened and i truly thought brittani would die. >> the sisters rushed to the hospital but once then, they were met with confused looks. >> they are, like, brittani, we don't have a brittani marcell. >> putting brittani under an assumed name was a smart move, because then the family was told about a visitor waiting to get into see brittani. >> i said do you know a man came in to see her? >> who? >> we don't know. >> the man left before he could be identified, and diane had a terrifying thought, maybe it was brittani's attacker? >> i didn't know if this person was watching us from a far, did he follow the ambulance, and i went to the rest room and i would look at the back of every door to make sure nobody was in there and standing on the commode. >> fear took over. >> fear. >> her family could only guess as to who attacked her and why? >> we started looking, who is in our lives? was it any of the boyfriends? >> everybody was trying to formulate as to who, how and when? >> the marcels, they were self-sufficient, and the children looked out for each other. >> how do you think it shipped brittani being number five in this big family? >> she looked up to kathleen, kristin and alicia. >> remind me who is the oldest? >> i am. i think i was her mom, too, and the littlest one has the most moms. >> like her oldest sisters, brittany was disciplined and hard working. >> she was an excellent student. she had a good circle of friends. >> i think she kind of set herself apart from the popular crowd rather than was inside it and that's because she's very genuine in everything she does. >> brittani was headed to college and hoping to be a tv reporter. >> she graduated high school early and she wanted to study journalism. >> but her mom, diane, said brittani hit a rough patch during her junior year in high school. >> how was brittani acting? >> rebellious. just like a 17-year-old, confrontational if you ask them something. >> so she moved in with her dad? >> and he was not there all the time, so it was perfect for her. >> by the start of her senior year, brittani wanted to come back, and that's why she and her mom were meeting for lunch to discuss brittani's return, and instead brittani was attacked. >> what did the doctors tell you when she was brought to the hospital? >> she would not survive. >> were you able to see her? >> we could see her but she doesn't know. >> brittani's head was the size of a basketball if not bigger. i don't think any of us thought, that's brittani. >> what goes through your mind when you realize you may never have any moments with your sister again? this could be it. >> the moments you missed. brittani had a couple nights before asked me to go to a maroon 5 concert, and i was too busy and i didn't tell her i loved her enough, and she didn't know how much she meant to me and i didn't tell her how much i appreciated her, and my son will not see her again. >> you are having a rehearsal for a death that has not happened. >> coming up, who was brittani's attacker? >> this seems so personal . >> this person seemed like he was full of rage. >> who was he? >> we never experienced that kind of imminent danger -- >> when "dateline" continues. >>s e fund, we are giving back by reseeding native wildflowers and grasslands. learn more at airwick.us nexgard is the #1 vet-recommended flea and tick protection, and it's easy to see why. it protects for a full 30 days, prevents the infection that causes lyme disease... ...and is safe to start protecting puppies as early as 8 weeks. but your vet doesn't just prescribe it to her patients... ...she also trusts nexgard to protect her own dog. and she knows that its beef-flavored deliciousness makes it #1 with dogs. ask your vet about nexgard, and why it's #1 with pretty much... everyone. and why it's #1 (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. introducing the new sleep number 360 smart bed. it's the most comfortable, dually-adjustable foot-warming, temperature-balancing, proven quality night's sleep we've ever made. and now, save up to $500 on select sleep number 360 smart beds. plus, free premiumdelivery when you add a base. ends monday. when you switch to xfinity mobile, you're choosing to get connected to the most reliable network nationwide, now with 5g included. discover how to save up to $300 a year with shared data starting at $15 a month, or get the lowest price for one line of unlimited. come into your local xfinity store to make the most of your mobile experience. you can shop the latest phones, bring your own device, or trade in for extra savings. stop in or book an appointment to shop safely with peace of mind at your local xfinity store. >> reporter: while the marcells tried to grasp what happened to brittani, the police were trying to find out who did it. albuquerque police detective jason morales was the lead investigator. >> reporter: you've seen a lot of murders in your career. how -- how brutal was this attack in this house? >> it was very brutal. >> reporter: morales said brittani had been hit repeatedly with a shovel, so hard it crushed the left part of her skull. >> when i got here, the crime van was already parked out front. they had been here for a little while. they were waiting on the condition of the victim, brittani, to see if she was going to survive or if she's gonna die. >> reporter: morales said the fact brittani's purse and sunglasses were found right in the entryway led him to believe the attacker came up behind her as she entered the house. >> reporter: did you get the sense that maybe this was a burglary in progress and brittani just happened to come home? or do you -- did you feel like the perpetrator was someone that brittani knew? >> this just seemed so personal. it seemed, to me at the time, that we're looking at somebody that either knew brittani or knew somebody in the family. or there was something -- there was more of a connection to there. >> reporter: the brutal nature of the attack, did that tell you anything? i mean, this person seemed like they were full of rage. >> it does. we started trying to figure out who was brittani hanging around with? who might be a suspect 'cause it really -- at this point, we had no suspect at all so everybody is. >> reporter: morales believed the attack had just started when brittani's mom arrived. >> i don't think he was -- anticipating diane showing up. >> reporter: the pattern of blood at the scene indicated the attacker actually chased diane when she fled the house, but stopped for some reason. maybe, morales thought, when diane started screaming. >> and he panicked. so instead of going out a sliding glass door whether it was locked or unlocked, he jumps out of a dining room window, i mean, not through the screen, he jumps through the glass to get out. >> reporter: inside the house, morales found a room full of evidence. >> so once we were able to go inside, you could see it was pretty violent. there was blood on the floor. a shovel. there was duct tape. and, then, there was also a knife. >> reporter: a lot of clues. >> yes, absolutely. >> reporter: enough, morales thought, to solve the case. that is, until he got the lab results. the fingerprints found on the shovel, knife and tape were incomplete. dna from a male was found on the shovel and the knife, but it was so intermingled with brittani's blood, it was impossible to develop an individual profile. but on a shard of broken glass, police found a drop of blood that looked promising, because it was pristine. >> when he jumped out of the window, he cut himself. >> reporter: the blood drop was analyzed and a complete, male, dna profile was generated, which morales uploaded to the national criminal data base, called codis. >> to see if it would match anybody that's already in the database. >> reporter: did you get a match? >> no. >> reporter: no match? morales couldn't believe it. he was convinced brittani's attacker had to be a repeat offender. >> you'd have to figure that somebody that's done something in that extreme has done -- done something like that before. >> reporter: brittani's attacker, basically, vanished into thin air. >> yes. >> so now morales' investigation went from the lab to the street. he'd heard brittani was seeing someone, kind of a boyfriend. >> reporter: was he a potential suspect? >> absolutely. >> reporter: did you do a dna test on her s -- sort of boyfriend? >> yes. he was cleared. his dna did not match that. >> reporter: police didn't have to rely on just hard evidence, though. they had an eyewitness to the attack. >> i could see his height. reporter: brittani's mom had actually seen the guy. >> i saw he had jeans on. he had a long-sleeved shirt on, >> reporter: and what does he look like? >> either a dark caucasian man or a light hispanic with brown hair, kinda spiky. >> reporter: police created a composite sketch and spread the word across the rio grande valley. >> there was both billboards, rewards, crimestopper's rewards. names just start pouring in. so we were talking to a bunch of people. >> reporter: but to no avail. the billboard campaign didn't produce any workable suspects, witnesses or leads. meanwhile, the marcell family was on edge. in the days following the attack, brittani remained on life support, close to death. >> we really didn't know what to do when they said, "she's probably not gonna make it." >> reporter: their home, once a safe and sacred place, was now marred by evil. >> walking in was like someone died there. like, it was just morbid. >> it -- it was just dark. >> hard. >> very dark. >> going back there, it's a dark feeling you get on the inside of this is not okay and you just want to get what you have to get to survive and leave. >> reporter: brittani's mom soon found a rental house, but changing addresses didn't help with the lingering unease. >> whenever we're in the house, the alarm was set constantly. no open windows. no open doors until we go out. our whole lifestyle changed. >> reporter: the marcells were terrified brittani had been attacked by someone who knew them and their routines, someone who might strike again. >> we just never experienced that kind of imminent danger. >> i think it was unsettling for everybody. and i think they had every reason to be worried. >> reporter: they worked out a schedule, taking turns standing vigil at the hospital with brittani. they tried to be hopeful, but they also knew the doctors and the police all thought brittani was going to die. >> and all the reports at the hospital were looking -- like, the trajectory was for brittani to pass. >> reporter: but, somehow, brittani held on, and six weeks after the attack, against all odds, she finally opened her eyes. >> when brittani came to and she woke up, her eyes were blue like the ocean before. and they -- they were gray. and i kept thinking, "he took your light, oh my god, he took your light." >> reporter: and in brittani's new, gray eyes, her family saw something else, fear. coming up -- >> who is this guy that hurt me? why did he hurt me? >> reporter: brittani and her family still haunted. >> your friends, your teachers, your boyfriend. >> reporter: so everybody's a possible suspect? >> it sounds crazy but it could be anybody. >> reporter: when dateline continues. ve skin. that's why we always look for new tide hygienic clean free. it goes deep into fabrics, to remove the visible and invisible dirt. and, it's designed for sensitive skin. hey! what's that? it's got to be tide hygienic clean free. hey shaq, remember you were talking about the general being great insurance and we stopped letting you sit with us at lunch? i do. well turns out you were right. they're actually a quality insurance company. that's what i've been telling you. can we sit with you? *sips* ahhh. for a great low rate, and nearly 60 years of quality coverage, go with the general. >> reporter: brittani's beating was so horrific, we created sketches of her time in icu rather than show you the actual photos. part of her brain was removed, then she contracted meningitis which nearly killed her. one surgery after another. but brittani held on. and by christmas, three months after the attack, the family was told brittani would survive. but what would her new life be like? >> we talked to her, and she would blink her eyes and smile, but we knew at that point, her -- there was a lot paralysis. and that's when they told us her ear canal is crushed. she's going to be deaf. they also told us that her optic nerve is probably atrophied, which it's severed, just from the hitting of the head, the jolting of it. >> reporter: despite her extensive injuries, brittani's family started taking her on short outings. >> and we put her in the wheelchair and she still couldn't hold her head up. and she's drooling. i was like, "please don't let this be it." >> reporter: the family knew this might be all they could hope for. >> there was so much dead tissue in the front temporal lobe. they removed pieces of that. and they -- with the brain they were saying it's so unpredictable. that could be any -- >> your short term -- >> that could be your speech. that could be short term. it could regenerate. >> reporter: as they tended to brittani, her sisters continued to wonder who could have done this to her? >> it's violating because you start questioning relationships you trust. >> exactly. yes. >> at school, your friends, your teachers, your boyfriend, your circle of influence. you're like, "well, maybe it was you." >> reporter: so everybody's a possible suspect? >> even going to the gym, going to the grocery store, you know, standing at the gas station, i mean, it's -- it sounds crazy. but when you don't know who it is it could be anybody. >> uh-huh. >> reporter: it was all so personal. the attacker had been in their home. possibly stalked them. maybe brittani wasn't even his intended target? maybe it was one of the other sisters. no one could say for sure. but the family had to put their fears aside when caring for brittani, who now needed all of their help. >> it's really taking your baby and raising her all over again. so you're raising a child that you already raised. >> that, i think, was the hardest part, watching mom have to go through that again. you just -- you wanted to cry for them. >> reporter: five months after the attack, her condition had stabilized to the point brittani could be released from the hospital. but she was far from healed. >> she didn't realize why she couldn't walk, why she couldn't eat, why she had to learn all these things over again. >> reporter: as helpless as a child, which meant if the attacker returned, the marcell family was more vulnerable now than ever. so diane fled albuquerque, taking brittani along with the two youngest children to neighboring texas. she found a new home, a new job, and most important a rehabilitation clinic for brittani. >> her mom was very, very anxious because we didn't know who the assailant was, and that they were still very concerned for her safety. >> reporter: doctor lori wright was one of brittani's therapists. what was your first impression of brittani when you met her? >> she just didn't know much beyond where she was. and she was very, very confused. crying a lot. she had to have somebody shower her. she had to have somebody take her to the bathroom. she had to have all those things done for her all over again. >> reporter: doctor wright, a neuropsychologist, practices what's known as "cognitive behavioral therapy." >> we believe with practice, practice, practice, the brain can heal. >> reporter: which means teaching a head trauma patient to do one simple task over and over again until it becomes reflexive. >> because their brain is just not the same brain that that used to be. it's -- >> reporter: is it like rewiring the brain? >> absolutely. it is rewiring the brain. and so what do you do? you sit down, you do it with her until she's able to do it herself. >> reporter: brittani's brain injury was so severe much of her therapy was almost like a pre-school class. >> she would read her dr.seuss books to me. and that was a rehab. and she would have to read. and i'd read, and she'd read. it's like reading to a toddler all over and teaching a child to read. >> reporter: but the attack on brittani was so brutal, dr. wright wasn't sure how far she'd get in her recovery. >> there was 25% of the brain she wasn't able to access that she used to be able to access. >> reporter: did you think she'd ever get her memory back? >> getting that memory back, most people don't ever. especially if it's a traumatic brain injury, if you're -- you don't usually remember. >> reporter: if brittani's memory did return her account of the attack could later be used as evidence. so dr. wright didn't give brittani any of the details out of concern it could create false memories. >> when people come out of this kind of trauma, they're not sure if this is a memory that they're remembering, or this is something that somebody's told them. >> if her memory were to come back, we wanted it to just be her memory. >> reporter: as she slowly learned to talk again, brittani seemed stuck in a loop of fear. >> she would -- just on repeat, you know, "i'm afraid, i'm afraid. who is this guy that hurt me? why did he hurt me? and you know, what am i going to do if he comes to get me