03/13/2014 09:01 EDT | Updated 05/13/2014 05:59 EDT

Dr. John Bradford won’t work Magnotta case because of PTSD

One of this country’s top forensic psychiatrists says he will not work on the upcoming trial of alleged killer Luka Rocco Magnotta because he suffers from post traumatic stress disorder, a condition triggered by a career spent absorbing graphic video evidence.

Dr. John Bradford said he never used to believe PTSD was real, but having experienced it, he now recognizes that it is a true medical condition.

“I’m not a skeptic anymore,” he said. “I can tell you it’s real.”

In his career, Bradford analyzed some of Canada’s most notorious murderers, including Paul Bernardo, Karla Homolka and Robert Pickton.

But he says it was the case of convicted killer ex-colonel Russell Williams that triggered his breakdown.

“It’s like a switch went off in my head and I just broke down,” Bradford said. “I get tears occasionally, but this was sobbing, out of control.”

‘It was just eating me up’

Bradford had spent days interviewing Williams, the former Canadian Air Force colonel who pleaded guilty in 2010 to 88 charges, including two murders, two sexual assaults and dozens of break-ins or attempted break-ins into women's homes.

“He wasn't a psychopathic individual who suddenly at 45, 48 years of age started to kill women,” Bradford said of Williams. “Something happened in his life, which has never been in the public domain, I’m not at liberty to talk about it, and that made a change.”

Bradford said it was the videos of Williams raping and murdering his victims that gnawed at him.

“You are looking at these videos as they are unfolding. You are hearing what the person is saying, you are seeing the interaction and you know what the end result is,” he said. “It was just eating me up.”

Considering himself a “tough guy,” Bradford said he tried to work through his distress. It didn’t work. He started drinking, became irritable and even considered suicide.

With medication and therapy, Bradford says he is now feeling better. But after initially agreeing to work on the Magnotta case, he has since changed his mind.

Magnotta will stand trial in September for the 2012 death of Concordia University student Jun Lin. The case involves murder and dismemberment, all of it apparently videotaped.

“I’m getting old now,” Bradford said to explain his decision not to consult on the Magnotta case.

“I don’t need to do this stuff anymore. I think for now I will probably avoid it.”