Transcript for Brother of murdered Tenn. student recalls the last day he saw his sister alive
Reporter: A patchwork of dense woods and hardscrabble farms sewn to the west bank of the Tennessee river. This is Decatur county, Tennessee -- atvs, horses and hunting. It's where Karen and Dana Bobo live. In a home they built with own hands, with their 25-year-old son Clint, and his younger sister, 20-year-old holly. Holly was pretty much a mother's girl. We shared a bond that she would sometimes look at me and say that it's scary, because we could finish each other's sentences. Reporter: Whitney Duncan, a country music singer, is holly's cousin. She had a beautiful voice, so I would kinda help coach her a little bit on that. ??? Will will be peace in the valley for me ??? Reporter: And it was a special time for holly, she had recently received a promise ring, from her boyfriend, drew Scott. And I remember her showing me and just being so excited about the future. She really was planning their life together. Reporter: The last day of her life was a Wednesday. A perfectly ordinary April morning in 2011. Too early for trouble. The sun climbing the trees, chasing off the mist. The Bobo family is rising too. Holly, a nursing student is up by 4:30 that morning, studying for her test that day. Karen packs holly's lunch and then she's off to teach second grade at Scotts hill elementary. Reporter: Did you say goodbye before you left? She was sitting at the kitchen table. Studying and I kissed her goodbye and told her I loved her. Just like every other morning. Reporter: Holly gathers her lunch and homework and walks out to get in her mustang in the carport. At about 7:40, holly's older brother, Clint is asleep in his bedroom, the house is quiet. Until the scream. Around 7:40 that morning, a neighbor was getting ready to go to work, and was outside and he heard a scream from next door. Holly screamin', "Stop, stop, stop it!" Reporter: Her brother Clint doesn't hear holly screaming, he wakes up to the family dog barking. So I decided to get up. See what he was barking at. Reporter: Clint hears voices in the carport behind the house. I listened just briefly, and I could tell it was a male, and a female voice. I never was really able to tell what they were saying. Reporter: You couldn't tell if they were shouting, if they were arguing? Well, as I listened a little bit closer, I could tell that, that was holly's voice. So I knew it was holly, so in my mind the males voice I knew to be drew, you know, who was her boyfriend. Reporter: Through the blinds, he spies the strangest thing, two figures in the shadows of the garage. Holly was knelt down in the garage, and a man in camouflage who I identified as drew were knelt down in the garage facing each other. Reporter: Unsure what's going on, wary of walking into the middle of a quarrel between holly and her boyfriend, Clint calls his mother. And he asked me, "Was holly not going to school today? Was she going home with drew?" And I says, "That's not drew." Reporter: Karen Bobo knows holly's boyfriend is elsewhere that morning, Turkey hunting. So I instantly knew something was wrong. I could see them just briefly. Reporter: Where were they? They were walking towards the woods and there's a trail, leads you to a logging road. Reporter: Was your sister walking unaided? On her own? Yeah. She was walking on her own. Reporter: So he wasn't dragging her? Oh, no, no. So when Clint told you on the phone, "Holly and drew just walked off into the woods." I said, "That's not drew. Get a gun and shoot him." And Clint said, "You want me to shoot drew?" And I think that's when I hung up and called 911. 911 what's your emergency? I am in a full-fledged panic by then. Somebody has my daughter, please get there now. Reporter: Police rush to the house on swan Johnson road, followed closely by Dana and Karen Bobo. I ran through the woods calling her name. Reporter: In the garage there's evidence of a struggle, a puddle of blood later confirmed to be holly's. Holly's nursing school classmate Suzanne Pratt knew something was wrong when holly didn't show up for their test. We waited for just a little while, because she wasn't there and no one knew where she was. Reporter: Then the instructor broke the news. She announced that something terrible had happened. Soon half the county, people, police, and search dogs overrun the Bobo property. Get ready to go out into the woods, okay? You had neighbors, friends, family, all of Decatur county, just kind of poured into this family's front yard, and they're out in the woods looking for her. You know, cops everywhere, helicopters flying. It was already crazy. Reporter: Holly's dad tells reporters he suspects the man who took holly had to be familiar with the area, familiar with her habits. It might've been somebody close. Somebody that kinda knew our routine, when I left, when she left, and when my daughter left to go to school. If you see anything that's not right tell me. Reporter: Tennessee, the volunteer state, lives up to its name. Day after day friends, neighbors, and strangers continue searching for holly. Reporter: The urgent search for a young woman gone missing. Holly, I love you so much. Please, please try to get home to us. We've been searching all day and pretty well into the night. Reporter: Police ask AT&T to track holly's cell phone. Reporter: What could you tell from holly's cell phone that morning? Essentially, for an hour and a half, her cell phone traveled all through Decatur county. Reporter: The beating electric pulse of holly's phone travels north to a wooded area near interstate 40, and then turns back south by another route. At any point does the cell phone stop moving? Around 8:30 to 9:00 that morning, her cell phone stopped moving for about -- about 20 to 30 minutes. And what do you think was happening at that point? I -- I don't wanna think about it. Reporter: For several days the house is a crime scene. Eventually the Bobo's are allowed to return home. I remember the, you know, the first thing I wanted to do was go to her room and open her closet and smell her. Reporter: Karen Bobo longs for the touch her daughter's hand. When holly was at home, you know, she'd be asleep. Her hand would be kind of folded like this, and I would just slip my hand in her hand, for just a few seconds. And I remember doing that after, trying to feel her. Thinking if I could just feel her hand in my hand. Reporter: Investigators follow every lead. Disheartening evidence of holly begins turning up -- homework, a notebook, that lunch her mother made, and holly's phone, all found scattered along backcountry roads in the weeks after the abduction. I wondered if she maybe had a chance to throw out some things, or if it was just some kind of taunting. Reporter: The strange abduction, the apparent signs of familiarity with the victim, and the trail of evidence, lead police to think the suspect was close. Perhaps even inside the house! There were a lot of people that felt Clint was lying. Reporter: Holly's own brother, what does he know? Have you told everything you know about that morning?
This transcript has been automatically generated and may not be 100% accurate.