The case stuck with the Plantation native and Florida Atlantic University grad, who was astonished it had flown under the radar for so long. By 2010, he found himself using his downtime at work searching online databases and public records for names of potential suspects. He shared his theories on an online forum maintained by A&E, which was packed with people just as obsessed as he was.
"It was something that I was embarrassed about; it was something I didn't talk about with people," says Haynes, who is now 36. "When I went on first dates, it was something I kind of withheld because it's a strange kind of preoccupation."
But that strange preoccupation would lead him down an unlikely path to a partnership with true-crime writer Michelle McNamara, a move to Los Angeles, a best-selling book, and now an HBO show.
That part of the story is better known: McNamara,
It was on the A&E forum that Haynes first connected with McNamara, who nicknamed him "the Kid." Both had long been captivated by unsolved crimes ("Each case represents a puzzle with a real-world solution," Haynes says), and especially by the case then known as EAR-ONS, short for the East Area Rapist-Original Night Stalker.
The killer would slip into his victims' homes at night and wake them with a flashlight. In the early years, he would rape the female victims while leaving the men tied up. Later, he moved on to murder. He vanished after 1986.
McNamara and Haynes, who was spending as many as 15 hours a day mining data for clues about the killer's identity, began writing back and forth and swapping theories. It turned out he and McNamara, whom he knew from her blog, True Crime Diary, had some similar ideas.
"We always felt the case was highly solvable; it was inevitable that it would someday be solved," he says.
In 2013, McNamara wrote a story for Los Angeles Magazine about her search. Haynes wrote an accompanying piece. Soon after, she began working on a book about the case and asked him to be her lead researcher.
Haynes pored over maps of California,
One day, Haynes emailed McNamara his thoughts on a file she'd sent him from that mother lode. She didn't respond to that message, or to another he sent about something else. Later that day, one of McNamara's friends told him she had passed away that morning.
"When it finally broke the next day, that confirmed that it was something that really happened, not something I had just dreamed," Haynes says. "It was the last thing I expected would happen."
The book had to be finished, he and Oswalt and Jensen decided. They spent about a year and a half working on it, patching the holes and preserving the general shape and tone. "I'll Be Gone in the Dark" became a number one New York Times
Then on April 24, after doing a book event in Chicago with Oswalt and Jensen, Haynes found out an arrest had been made. The next day, he saw for the first time the name and face of the killer he and McNamara had been pursuing for years.
DeAngelo, who was identified using DNA, had never been on their radar. Still, Haynes believes her work helped build awareness and open up resources that hadn't been available before. One of his first thoughts after learning the news of DeAngelo's arrest was how tragic it was that McNamara wasn't there.
"I think she would have a whole book full of questions to ask him," he says. "As do I."