On the morning of March 28, 2003, she says Ortralla went to school expecting trouble. Marcus was an emotional wreck, begging Ortralla not to leave him, Mosley says.
Ortralla's English teacher, Vanessa Connor, recalls that Ortralla seemed particularly distressed about Marcus. "I looked at her and she looked like she wasn't all with me that day, you know. And I said, 'Baby, you, you all right?' And she said, 'Oh, you know how it is, Miss Connor, roller coaster of love. You know how teenagers are.' And I smiled and said, 'All right,'" Connor said.
But things weren't all right. At 4 o'clock that afternoon, Marcus snapped. After a violent confrontation, he chased Ortralla to a second-floor hallway, pulled out an 8-inch kitchen knife he'd hidden in his backpack and began stabbing her repeatedly: six times in the head, the neck and the back. Students and teachers heard screaming and came running.
Amid the chaos, Connor knelt down on the bloody floor to provide comfort to the dying girl. "I was saying, you know, 'You got to hang in there. You got to stay with me. Don't go.' And it was the hardest thing I've ever been through," Connor said. Moments later, Ortralla was dead.
Marcus was arrested and charged with murder. He pleaded guilty and is now serving a 40-year sentence.
Marcus declined requests for an interview, but "20/20" was able to speak with another young man who says he understands how teen dating relationships can become physically abusive.
Chris Cummings, 22, does not know Marcus, but says he understands how the cycle of abuse can poison a relationship. Cummings said he had a deep-seated insecurity as a teenager during a three-year relationship.
Cummings said he didn't hit girlfriend "with a fist," but he'd push her around. "I threw her to the ground once or twice," he said.
When his girlfriend cried, he said, the violence would escalate. "It just made it worse, you know, 'cause then I'd hit harder," he said.
Cummings says violence somehow made him feel powerful and in control. He even took out his frustrations on his bedroom walls.
Murray says that's a classic sign that a teenage boy may become abusive.
"A boy who puts his fist through a wall or through a window is a dangerous person, because the brain doesn't know the difference between a wall and a face. All it knows is that when I punch through something, I feel better. And then the next step is he punches them," she said.
Cummings says he is grateful that his relationship never descended as far as Marcus and Ortralla's did. He realized he needed help and got counseling with the support of his family. Unfortunately, in the case of Marcus McTear, his uncontrollable violence left Ortralla dead and Rae Anne emotionally scarred.
"I have nightmares of the murder. I feel like I was there, even though I wasn't," Rae Anne said.
Rae Anne said she still struggles with self-esteem and confidence issues. "Marcus still has a lot of it. I just hate that he has half of me with him. The me that I want back," she said.
Now 19, and wiser, Rae Anne is refusing to run away from her past. She's speaking out, hoping to spare other young girls from the nightmare that she escaped and Ortralla Mosley did not.
She said she keeps a picture of Ortralla above her bed. "I feel like now I'm not just living for me, I'm living for her," Rae Anne said.