Transcript for Former track star says coach threatened her with a box cutter to her throat: Part 3
Reporter: This looks like an ordinary office but baillie Gibson claims for more than two years it was a place of torture where her coach Craig Carter coerced her into countless sexual encounters. Baillie tellu no one. She turns to food to help her cope. I ate. That's my comfort as eating. That's kind of my comfort is eating, and I got heavier, and I didn't really sleep a lot, so I was very depressed. I had to act somewhat Normal, but inside I was just dying. What was the lowest point for you? When I was totally done with like everything. I didn't want to be an olympian anymore. I didn't want do track. I didn't want to go out with my friends. I didn't want to do anything. Reporter: Then by happenstance the secret begins to unravel. In November of 2013, a female track and field staffer knocked on Craig Carter's office door. It was locked. He took a long time to come to the door, and when he finally did emerge, his clothing was disheveled, and baillee Gibson was sitting on a couch in his office. She grew concerned that something inappropriate was going on inside the office, and so, she reported it. Whether consensual or otherwise it is strictly forbidden according to the university of Arizona policy, which states, no university employee shall engage in a romantic or sexual relationship with a student, and any violation of this policy is subject to disciplinary action including discharge. Reporter: Craig Carter was called into a meeting on November 5th of 2013 with his head coach, Fred Harvey, and the athletic director at the time, Greg Byrne. ESPN investigative reporter John Barr obtained this memo where school attorneys advised Byrne the athletic director to say the following to Carter. Coach, we have received reports of information that may indicate you are having or had a romantic or sexual relationship with a student athlete on the team. In the column of the notes, he writes, baillie Gibson. Reporter: During that November 2013 meeting, coach Carter lies, adamantly denying a sexual relationship with baillie Gibson to his superiors. There was no further investigation of him. According to Craig Carter, that meeting was the last of it. He denied it, and that's where it ended. They never asked to see his phone that was issued by the university. They never looked at this university email account, but they asked Craig Carter, what will baillie tell us if we talk to her about what happened? What will baillie say? Turns out, she says Carter got to her before the university did. Craig called me, and said hey someone saw something, you better not answer anything. He's like, don't say anything. So the coach is telling you not to cooperate. Yes. Don't say anything. Yeah, and if you do, tell them that I was just comforting you that day. So the university now is aware of this relationship. Do they contact you? They emailed me, but they did not confront me in person at all. Reporter: Here are the two emails baillie says she was sent from the school's anti-harassment office, informing her they received a report that she may be involved in a personal relationship with an employee of the university, and listing campus resources she could contact if she wants assistance. Baillie never responds. And you don't reply. No. Why not? Well, how am I supposed to? He told me not to. He knew that the e-mail was coming. But this is a chance for you to blow the whistle on him. But what I if I do and he decides to retaliate. Am I going to be protected? Reporter: But instead of messaging the university, baillee continues messaging her coach, not only about practice, but something much more graphic, explicit images of herself. Carter claims she sent him dozens of naked pictures and pornographic videos. Why are you doing that? Because to some people this looks like a girl who's trying to come onto her coach. Because it's easier for me to do that than actually have to have intercourse with him, and if he liked what I sent, then I didn't have to have intercourse with him. So this was purely a, a sexual relationship based on blackmail. Yes. Reporter: For the next 16 months baillie says she continues to suffer in silence until she reaches a breaking point, and begins sobbing in this campus parking lot to her best friend, and teammate Julie Labonte. I asked her, why are you crying? Because she's a very, very strong woman. Usually she doesn't show a lot of emotion. So I knew that deep down there was something very deep that was going on. Reporter: Julie keeps pressing. Was it a relative, an ex-boyfriend? And then I mentioned Craig's name, and she started crying even more. Then that's when she told me he had naked pictures of her on -- if you say anything, something bad will happen to you. This is your best friend revealing to you that she's essentially being blackmailed into sex. It was very, very tragic. I was in shock. I was so mad. I'm her best friend and I lived with her, and I didn't see those signs. Reporter: But instead of going to the authorities baillie decides to confront coach Carter herself. Less than a month away from graduation, she says she decides to tell coach Craig Carter she will no longer give into his sexual demands. I go to his office, and I say, I'm not going to do this anymore. You can hurt me, but I'm not going to be this person to you anymore. Like, I'm done. I said I've never loved you, and he got mad, and that's when he put his hands around my neck, went with a box cutter to my throat, said I'll kill you right now. He grabbed you and put a box cutter to your throat? Yes. What's going on in your mind? I'm not going to make it alive if I don't say what he wants me to. Reporter: Baillie says she'd never seen that aggressive behavior in her coach, and decides the only way to avert disaster is to back down, and apologize. I knew if I didn't say I'm sorry, and I would die right there. Reporter: Next, coach Carter goes from a box cutter to a shotgun. I know exactly where you're going to be, every day. With a shotgun loaded coming right at you? But baillie Gibson's armed with powerful weapon of her own, a cell phone.
This transcript has been automatically generated and may not be 100% accurate.