(CBS 8) - A former close friend of accused killer John Gardner has come forward with shocking revelations about his past.

Jennifer Brandt and Gardner weren't close in high school, but became friends shortly after they graduated from the Class of 1997 at Rim of the World high school near Lake Arrowhead, California.

"He was a fun and crazy guy," Brandt said.

That was the John Gardner who Jennifer Brandt thought she knew, until his 2000 conviction for molesting and assaulting a 13-year-old girl.

"Pretty much all of his friends were hurt and betrayed by him after that.  We stopped all contact with him," Brandt said.

She hasn't spoken to Gardner since then.  In fact, she says she hasn't even thought of his name in years, until he made national headlines.

"It was shocking. This was a guy I hung out with, I stayed the night on his couch," she said.

She told News 8 on the phone from Indianapolis that John once admitted to her a dark secret.

"He had on one occasion spoken to me about how a male family member had sexually abused him when he was young. He was almost in tears talking about it. I don't even remember how the subject was brought up but it was obviously something he needed to talk about, and I was there to listen," she said.

Gardner is accused of raping and murdering 17-year-old Chelsea King, and a suspect in the murder of 14-year-old Amber Dubois as well.

"It's very painful right now.  We had several very deep conversations," Brandt said of her former friendship with Gardner.

She says Gardner admitted he had major mood swings and claimed his mother once committed him to a mental hospital.

On one occasion, she and her friends watched from a car while Gardner streaked a convenience store, Brandt told News 8.

"He got completely naked and put a bag on his head and ran in the store.  And the thing that was funny was, there was nobody in the store.  The clerk was in the back," she recalled.

Gardner also threatened suicide a couple years after high school when his then girlfriend Jennifer Tripp dumped him, said Brandt.  Tripp is a couple years younger than Gardner and was still in school at the time of the breakup, according to Brandt.

"He missed her and he would cry about it and there was nothing left to live for without her," Brandt recalled Gardner telling her.

Brandt also believes Tripp – the girlfriend who broke Gardner's heart -- resembles both Chelsea King and Amber Dubois.

"From the photos that I see… the blue eyes, the straight hair… they all look like the girl he dated in high school and broke his heart," Brandt said.