"It probably was the drugs," he said. "I was just knee deep in trying to medicate myself and not feel, and numb myself to whatever I was dealing with."
In late 2010, Coleman, then 37, couldn't bear it anymore. He went to the police and told an officer he had shot a man 16 years before.
The police did nothing.
"I guess he just felt like it was so outlandish, so he was like, 'Listen, that was a long time ago. Give me your number and I'll call you,'" Coleman said.
Two weeks later, he went back to the police to confess again.
"I think I was just at a point where enough is enough," Coleman said. "It never went away, me thinking about it, so it was like I had to do something about it."
His memory of the incident was vague. He told police that he remembered the victim as being a light-skinned male standing at the corner of Park Avenue and 114th Street. He didn't know the date. The police soon found a match to a cold case murder of a man named John Henkel, who had been shot on Oct. 19, 1993 at that location. It was then that Coleman learned the man he shot had died.
Suddenly, he was charged with murder. But when asked if he had any second thoughts about turning himself in, Coleman said, "Nah."
"In the back of my mind I knew that 'what if' was always a factor," he said.
Once he resolved to confess his crime, his family was in disbelief.
"I was like, 'No, that's not Trevell,'" Sutton said. "That's not even in his character to do that. He's a kind, loving person."
After the case was made public, Sean Combs talked about it in December 2010 on Sirius XM Radio's "Shade 45."
"G. Dep is one of the nicest artists I ever worked with. ... You could always feel like ... something was troubling his soul, because he was real quiet," Combs said at the time. "But he's the type of guy who wouldn't hurt a fly. ... He did the right thing and manned up to it. But my prayers go out to him. He had a real bad drug problem and that could have caused that situation."
Jim Nelson, the editor-in-chief of GQ magazine, served as the jury foreman in the murder trial of John Henkel and has written about the case.
"You have to concede that that man probably lived in a jail in his house in his head for 18 years," he said. "The hard part about this case is that it involves a guy who didn't really need to come forward, who did. I mean, he needed to come forward for his conscience, but we were wrestling with this as jurors because we kind of thought, 'Why did you come forward?'
"Our mission is very, very specific: Is this guy guilty? And I wrestled with that because I knew. I knew he was. I just didn't almost feel worthy of passing judgment on this guy," Nelson added. "He did kill. I don't go into this with rose-colored glasses. I completely understand that for the people who knew John Henkel, it's a different story, and we have to keep that in mind."
The jury found Coleman guilty of second-degree murder. On May 8, 2012, he was sentenced to 15 years to life in prison. He was 38.
"The case of Trevell Coleman has haunted me," Nelson said. "I think the guy got a bad shake. I think he did something honorable and society punished him for it."
Coleman separated from his wife in 2008, but Sutton said she is still standing by him. She said she is still in doubt her husband shot Henkel, but he is now a different man.
"It's a different Trevell to me, not on drugs. He feels freer and that you can tell by talking to him," she said. "He sounds a lot better, like the Trevell I first met -- caring, loving, trying to do what he can."
To the people who might not understand why Coleman turned himself in, including some of the victim's relatives, Coleman said it doesn't matter because he is at peace.
"I don't feel like I'm cheating life too much anymore," he said "A lot of the burden is lifted, you know what I mean? And that was what I needed to do."