(KPIX 5) — A Bay Area detective was one door-knock away from cracking the Golden State Killer case on his last day on the job.

Retired Contra Costa County cold case investigator Paul Holes spent 24 years trying to track down elusive serial killer and rapist also known as the “East Area Rapist,” suspected in at least 12 murders, 51 rapes and dozens of burglaries across California in the 70s and 80s.

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The day before he retired some three weeks ago, Holes said he drove to the home of Joseph James Deangelo, who at the time was one of several possible suspects.

“I was thinking, you know, what’s the likelihood this is actually the guy?” said Holes. “And I thought, I should probably just go knock on this guy’s door and chat with him a little bit, see if he’ll give me a DNA sample.”

Full Interview: Paul Holes on Golden State Killer case:

But Holes thought better of it and never knocked.

“In hindsight, he’s a very dangerous individual. He had a lot of guns registered to him. I was alone. It could’ve been a bad situation,” said Holes. “So fortunately, I made the right decision.”

Holes has continued to work with investigators, right up until their announcement Wednesday that Deangelo’s DNA matched that of the Golden State Killer, also known as the East Side Rapist. He says there are other details that match up as well. The Golden State Killer had been accused of saying a woman’s name during one attack.

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“He’s making the statement “I hate you, Bonnie. I hate you Bonnie” while he’s sobbing,” said Holes. “And so we always thought that there was a woman named Bonnie in his life that was significant to him.”

Deangelo was once engaged to a woman named Bonnie, according to Holes.

And then there are the reports of Deangelo’s temper. Neighbors and co-workers say he had an anger problem, which Holes says fits the profile.

“He’s what I would call an anger-retaliatory type of rapist,” said Holes. “He’s somebody that there’s a stressor in his life that makes him angry and instead of lashing out at what’s making him angry, he by proxy lashes out at his victims.”

Holes says identifying Deangelo has been an amazing feeling but what’s been even better has been talking to his victims.

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“Very rewarding to at least hear the relief in their voices that they can kind of now relax in a way,” said Holes. “This guy is behind bars. He’s never getting out.”