Break-up may have caused Golden State Killer to go on killing spree

LOS ANGELES (KABC) -- New details on the Golden State Killer investigation emerged and it may have been a break-up that sent the suspect on a killing spree.

Investigators are looking into Joseph DeAngelo's relationship with his ex-fiancee. The 72-year-old, who is now behind bars, is accused of 12 murders and dozens of rapes that happened all over California.

One of his victims in 1978, told police that during a violent sexual assault that her attacker repeated a name. Decades later, that name helped investigators home in on DeAngelo.

"He was sobbing and saying 'I hate you, Bonnie, I hate you, Bonnie' over and over. We run across a newspaper article of an engagement to a Bonnie in 1970, so now we have a guy that has a Bonnie in his life. So something happened in that relationship that caused them to part," retired investigator Paul Holes said.

A source told ABC News that Bonnie is Bonnie Ueltzen and she is speaking with prosecutors.

Prosecutors around the state are also sifting through cold cases to see whether DeAngelo is responsible for them.