We continue with the girl in the shower. Here again, David Muir. Reporter: For most families, new year's day is a celebration. But it would soon turn into the worst day of this mother's life. 12:24... See More
We continue with the girl in the shower. Here again, David Muir. Reporter: For most families, new year's day is a celebration. But it would soon turn into the worst day of this mother's life. 12:24 that afternoon, Kelly Osborn gets a call from Joe genoese, her daughter's fiance. He talked to Kelly and told her he was having trouble getting in touch with Sheena. She became concerned for her daughter and went to her apartment. Reporter: Then suddenly, that mother's cellphone ringing. The name that comes up offers hope. I answer the phone, and I go "Sheena, Sheena." And there is no answer. And now I am screaming into the phone, I am upset and calling for her. And then all of a sudden, I hear a man's voice in the background. Reporter: That voice, one of the police officers in her daughter's hotel room. It turns out, Kelly says, they inadvertently called her from her daughter's cellphone. That's when you knew something was wrong. That's when I found out something was wrong. Reporter: When police accidentally called you from her phone. They said, "We need you to give us your address" and I couldn't figure out why that was. Why would they need my address? Reporter: The finace, Joe, is summoned to Sheena's mother's house too. And when police arrive they tell them Sheena is dead. Found alone in that hotel room. Getting a notification like that is the most horrifying event you could have in your life. All we knew was that she was deceased. We didn't know how. Reporter: A mother begging for answers. I am asking them, "Well, where did you find her?" And they say that she was found in the shower. What we were thinking was, you know, did she slip and fall? Did she hit her head? Reporter: But the answer would be far more heartbreaking. The police never told us. So, when the medical examiner does call us and say, "We have just completed the autopsy, and it's consistent with a hanging," we are just dumbfounded. Reporter: Sheena was found with her clothes on, hanging in the shower, one of her precious dogs' leashes around her neck. And with no signs of a struggle in the room, and no obvious injuries to Sheena's body, the detective in the case Lenard Diaz and the police department quickly ruling it a suicide. Family and friends immediately argued it didn't add up. The moment I got the call, I knew that something was not right about the situation. Reporter: And Kelly says her daughter was hardly someone planning her own demise. The smiles in that video just days before. And so many other telling signs in the days before her death. She renewed a subscription to a magazine. Yes, she did. She renewed her aaa for the year. Reporter: Left her rent check. Yes. Yeah. Rent check is all filled out, ready to be paid, for the, you know, month of January. Reporter: And she says what also didn't make sense were those joyful text messages Sheena sent from that new year's eve dinner with Joe. And that night, Sheena's texting all her friends, she's all excited, saying, "I'm gonna be an auntie, I'm gonna be an auntie." Reporter: Kelly says she immediately wanted answers from one person. Three days after Sheena died, I had asked Joe to come out to the garage, that I wanted to talk to him. Reporter: And she delivered this message. This isn't over. Sheena didn't commit suicide. I said, "You can make this as easy or as hard on me, and yourself, as you would like." Reporter: Kelly was done selling houses. Now, a mother trying to solve a tragic mystery. I have every police report in here. Reporter: She studied hundreds of other suicides looking for patterns. And the one common theme that kept coming up. Drugs and alcohol? Yes. Reporter: And yet the amount of alcohol in your daughter's body -- -- Was under the legal limit, she could've legally driven, um, might have been one drink, two? Reporter: And any drugs? No, none. Reporter: And that was just the first discovery. She began poring over her daughter's cellphone records. And discovered a call to 911 that night. Not the one from the neighbors who heard that screaming, but it turns out there was also a call from Sheena herself. 9-1-1. What's your emergency? Hi, my name is Sheena. Reporter: Her mother says police never revealed that. I call detective Diaz. And he said, "Only the people in the room next door made a 911 phone call." I had to go and learn how to try to retrieve a 911 phone call. And when I did, I delivered it to detective Diaz. Reporter: Sure enough, it was her daughter calling after that argument with Joe. 2:10 that morning. He just made me bleed and left claw marks all over me and stuff. They had had many fights before. She chose to call the police on this particular night for a reason. This one had to be a big one. Reporter: And Sheena's mother discovered something else. The text messages her daughter sent Joe after that 911 call. 1:53 in the morning. You're evil and scary. Stop being an alpha male and stop putting your hands on a woman. And there were images too. How did you discover the pictures? They had released the camera to us. And that's where we found that she was actually taking pictures of herself, of what he did to her. Reporter: The photos on her camera showing a cut on her neck and a scratch on her finger. So the police, they'd never looked at the pictures. They knew what was in her camera. And they dismissed it. Reporter: And as Kelly quietly pored over every piece of evidence, there was someone else who got a tip. A reporter, a former cop himself, lee Williams. I had a call from a source in law enforcement, who said I needed to look at this case. I talked to Kelly, I was hooked. Reporter: You were? Yeah. Reporter: There were enough red flags right from the start? Right away. Reporter: Lee Williams has reported extensively on the case for the "Sarasota herald tribune," writing that the lead detective in the case had never been sent out on a homicide investigation alone before, asking how would he know if he were looking at one now? Any suspicious death should be initially viewed as a potential homicide. He walked in, he saw her hanging, and I think he just, in his mind it became a suicide. Reporter: Sheena's mother started calling that detective, convinced the investigation had been botched. I had called him, and said, "Have you questioned the boyfriend yet?" His exact words to me were, "No, why? Should I?" The detective waited 22 days before interviewing Joe genoese, during which any wounds or scratches that he had on his body could have healed. Reporter: Do they write up a report? No, they did not. Reporter: How do you not document that? I certainly would've documented that conversation, probably videotaped it too. Reporter: And the big question -- just where did Joe go after leaving the hotel room? He told police he went home and there were tenants in his townhouse who saw him. But Sheena's mother said police at first never went to check on that alibi. We reached out the Bradenton beach police department and to that detective. They've declined to comment. But the Bradenton beach police have long said they didn't rely solely on that alibi. They say they have cellphone records, pings from Joe's phone cell phone calls and text messages, revealing Joe's locations. In fact, they say those pings trace his route home. I've never seen the pings, they've been sealed by a judge, I'd love to see them. Reporter: You'll see them for yourself later.
This transcript has been automatically generated and may not be 100% accurate.