LOS ANGELES (KABC) --What triggered "Grim Sleeper" Lonnie Franklin to kill?
It is one question still hanging for the families of the convicted serial killer's multiple victims.
Noah Thurmond used to fix cars with Franklin and said the backyard mechanic could be pushy, but nothing indicated he was a killer.
"He was always advising me. I didn't want his advice. But as a person he was just normal," Thurmond said.
Fernando Cole said he knew Franklin for over 40 years.
They confided in each other, Cole said, and Franklin showed him the many photos he'd taken of partially nude women.
"It looked like they were drunk or dead or something," Cole said.
After Franklin was arrested in 2010, police found dozens of photos of women in his home and released many of them to the public in an effort to identify more potential victims. Investigators are still seeking public assistance with the photos, which can be seen here on the LAPD website.
Franklin was convicted in May 2016 of killing nine women and a teenage girl and was sentenced to death on Aug. 10.
In an LAPD interrogation video now made public, Franklin reacts to what police learned about his secret life. Photo after photo. Women dead. Many with Franklin's DNA.
"There is scientific evidence - all pointing the finger at Lonnie David Franklin Jr.," says one detective in the video.
Detectives learned then that Franklin was still married to his devoutly Christian wife of 32 years. Eyewitness News has learned that to this date she's never cooperated with police.
When Franklin was arrested, Cole thought it was maybe for car theft.
"Yeah I was suspicious but I didn't think he was killing or nothing like that," Cole said.
But then, Cole said, there was an incident at Franklin's home that changed everything.
"His first wife, she was on crack cocaine. He had given her money to pay the bills but he came home, there were youngsters in the house and she was there smoking crack. That's what set him off," Cole said.
Cole speculates that's what triggered Franklin's aggression toward women, from then on using drugs to lure many of his victims to his car.
It's a story investigators have never heard. And it does not explain Franklin's rape of two women in Germany in 1974 - 10 years before his first known murder.
Cole insists it is true. He now grapples with the mountain of evidence that convicted his friend, and that Franklin could carry out a murderous reign for decades without raising suspicion.
"My heart goes out to the bereaved families. If he did it, he deserves what's coming to him. They were innocent lives he killed," Cole said.