The woman, who asked that ABC7 News not use her real name, says Therrien and his partner were like family to her.
"I've always thought of him as being very kind, one of the kindest people I've ever met," 'Susan' said.
'Susan' knew Therrien, who police say had at least five aliases, as Kelly Jackson. She met him in 1979 when they lived on Masonic Avenue. Their friendship lasted a decade.
"They had me over all the time and they made me coffee and we used to hang out," 'Susan' said. "We were close."
Jackson was wanted in Canada under another alias for the 1973 kidnaping and sexual assault of two juveniles.
"He said he got into some trouble in Canada and so it was going to cause problems if he stayed here and used the same name," 'Susan' said. "He knew how to change his identity and how not to leave a paper trial, so I think they were conscious about living under the radar."
Jackson never told her he was a fugitive for molesting juveniles. 'Susan' says she didn't know for sure, but there were signs he might have liked young boys.
"He did tell me a story that had a sexual component in it about a young boy," she said.
'Susan' says Jackson told her about a boy who lived next door and that he looked out at the child's bedroom window and watched him explore his sexuality.
"And just the way he told the story made me go, 'Wow, that's made me feel a little uncomfortable and think this is a little over the line,'" she said. "He probably had some interest in young boys, interest in younger boys cause it sounded like to me the kid was younger."
Witnesses say they saw Kevin talking to ta tall blonde man with a dog. 'Susan' says Jackson was not tall and witnesses would have noticed another feature.
"He was maybe 5'6" maybe 5'5"; he was really short," 'Susan' said. "He had a big moustache. It was a predominant feature. It took up most of his face, so..."
Therrien, or Jackson as 'Susan' knew him, had been convicted and served time for performing lewd acts on a child at Fisherman's Wharf in 1981. Police interviewed him when Kevin disappeared, but they dropped him as a suspect when the witnesses could not identify him from a photo spread.
Therrien died six years ago.