Golden State Killer possibly motivated by breakup with fiancée, investigator says

When the investigators first questioned one early victim of the Golden State Killer in Davis, California, they weren't sure the woman had correctly heard what the assailant had sobbed as he raped her in the late 1970s.

"The original investigator asked her, 'Are you sure he isn't saying Mommy?'" Paul Holes, a retired Contra Costa County District Attorney's Office investigator closely linked to the investigation, told NBC News.

Bu the victim was adamant — the man who sexually assaulted her kept saying "I hate you, Bonnie," over and over again.

Officials now say that the man believed to be the Golden State Killer, Joseph James DeAngelo, might have been motivated in part by lost love to commit a lengthy string of rapes and murders through the 1970s and 1980s.

"We always thought that our offender had a Bonnie that was significant in his life, either a mother, a wife, an ex-wife, a girlfriend," Holes said. "We don't know, but that was something that we would look for when we were evaluating potential suspects."

DeAngelo, a 72-year-old former police officer, was arrested last week in Sacramento after DNA evidence helped police connect him to the decades old murders and rapes.

Holes said when investigators began looking into DeAngelo's background, they found a newspaper article from the 1960s about his engagement to a woman named Bonnie Colwell. The engagement never produced a marriage, however.

"So we assumed that there had been some breakup in their relationship and that possibly caused him some angst," Holes said.

NBC News was not able to contact Colwell, but NBC Sacramento affiliate KCRA spoke with her daughter, who said her mother plans to speak with the Sacramento County District Attorney.

DeAngelo eventually married another woman, Sharon Huddle, in 1973, according to the Ventura County Star. The couple has been estranged since the mid-1990s, according to the newspaper.

Holes said he doesn't believe DeAngelo is mentally ill, but instead classified him as "an anger retaliatory offender."

"This is an individual that [has] stressers in his life, people in his normal life make him angry and when that happens, he ends up taking his anger out on victims, ... and the instance where he is saying 'I hate you Bonnie, I hate you Bonnie,' — obviously, Bonnie is making him upset at that moment in time," Holes said.