After he raped Beverly*, the Golden State Killer lay his head onto the pillow next to her and began sobbing.

“I hate you. I hate you. I hate you, Bonnie,” he cried in 1978.

The name confounded investigators for the next 40 years as they frantically searched for the man who raped 45 women and killed 12 people between 1976 and 1986. On Wednesday, authorities said they caught the attacker, Joseph James DeAngelo, who reportedly was once engaged to a woman named Bonnie Jean Colwell.

She may have been the key all along, retired Contra Costa County investigator Paul Holes said Thursday. Holes told The Mercury News he’s now convinced that DeAngelo’s breakup with Bonnie and his reportedly “toxic” marriage to another woman fueled his alleged desire to rape and kill.

“We always thought there was a Bonnie significant in his life, it could be a mother, a wife, a girlfriend, a childhood crush,” Holes said.

DeAngelo met Colwell at Sierra College, where they attended school in the late 1960s. Their engagement was announced in the Auburn Journal in the late 1960s or early 1970s.

But the pair never married, and DeAngelo instead wed Sharon Huddle in 1973. The couple had three children before separating in the 1990s. Huddle’s neighbors told reporters that they had “epic shouting battles” that could be heard from several houses away.

When the Golden State Killer attacked couples, they were at home in bed: He raped the women and made the men listen helplessly to their screams.

“Most certainly if he’s making the statement, ‘I hate you, Bonnie,’ while he’s attacking another female,” Holes said, “he is what we call an anger retaliatory rapist,” funneling his anger at another relationship onto a stranger.

“I do believe that’s what happened here,” Holes said. “I don’t know what made him that way, but you’ve got to think Bonnie dumped him, he’s not happy about that, he still had feelings for her, who knows? But something along those lines must have happened.”

Beverly’s attack began the way most of them did. She awoke suddenly at 3 a.m. in July 1978 to a flashlight shining in her face.

“Don’t move or I’ll blow your fuckin’ head off,” stuttered the man in a ski mask, who had broken into in her home in a scenic Davis, California, subdivision. “I’m going to blow your fuckin’ head off, do you see this gun?”

The man also threatened to kill Beverly’s 5- and 7-year-old boys who were asleep in the next room if she didn’t comply with his orders, according to report from The Sacramento Bee at the time. She rolled over, and the man bound her hands and ankles.

Details of the attack are recounted in two books by former investigators, Hunting a Psychopath and Sudden Terror.

“All I want is food and money for my van,” the man said, as he tied a blindfold over Beverly’s eyes.

Then he ransacked the house and raped her. Afterward, he lay next to her and sobbed about Bonnie. He stole only $27 and some postage stamps before fleeing.

Beverly freed herself and ran to a neighbor’s home to call police. Authorities immediately linked the attack to a string of more than 30 rapes that had been committed in the Sacramento area. During some of those attacks, the assailant cried out about his mother.

“Nearly a dozen victims reported that he cried,” wrote Michelle McNamara, in her best-selling book I’ll Be Gone in the Dark. “He sobbed, they said. He stumbled and seemed lost. He whimpered in a high-pitched voice like a child. ‘I’m sorry, Mom,’ he wept. ‘Mommy, please help me. I don’t want to do this, Mommy.’”

A Davis police investigator reportedly asked Beverly, “Are you sure he’s saying Bonnie, not saying Mommy?”

“No, I assure you it was Bonnie,” she allegedly responded at the time.

It isn’t clear how or why her relationship with DeAngelo ended. Holes told The Mercury News that police haven’t been able to reach her, and she did not return phone messages left by The Daily Beast this week.

DeAngelo, 72, had been living a quiet suburban life outside of Sacramento for the past 30 years. After working as a police officer in the 1970s, DeAngelo spent most of the next three decades working at a SaveMart grocery warehouse before his retirement last year.

He was living with his daughter and granddaughter in Citrus Heights at the time of his arrest. He was also doing a woodworking project and making a roast. He planned to spend more timing fishing, his neighbors told reporters.

Investigators revealed on Thursday that they closed in on DeAngelo by matching DNA from an old crime scene to a genealogical database used by private citizens who submit DNA samples to learn more about their ancestry. Officials have said they used a site called GEDmatch.com to link the crime scene samples to a “distant relative” of DeAngelo’s. When they located the suspect, they allegedly confirmed the match using a sample of DNA “abandoned” by DeAngelo.

*Name has been changed to protect identity.