Old coworkers say the former cop was average, aloof and too serious.

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Old colleagues said he was aloof and overeducated. He didn't reveal a lot about his personal life, leaving his co-workers in the dark about his dark side.

Joseph DeAngelo, 72, was arrested on April 25 and has been charged with four murders as part of a California crime spree that included at least 12 killings and about 50 rapes.

Now details are emerging about his police officer past. From 1973-1976, he worked as a police officer in Exeter, California, a town of 5,000 with a police squad of less than a dozen officers.

"He was just over-educated for the small department of Exeter,” DeAngelo’s former coworker Farrel Ward told the Los Angeles Times. “He just knew anything you wanted to talk about. I think he had a bachelor's degree, all kinds of training.”

DeAngelo, did, in fact, have a bachelor's degree in criminal justice. He also fought in Vietnam as a Navy soldier, according to The Sacramento Bee.

“He didn't fit in with the other guys,” Ward said. “We liked to joke and screw around and take the stress off of what we were doing. He was always serious."

He told the Los Angeles Times that working with DeAngelo was pleasant but they never really bonded.

"I liked him, but he's not the type of guy that I'd have over for a barbecue. He's just … stand-offish. Too serious. Seems like he's always thinking," he said, adding that he never revealed much about himself. Ward did add that DeAngelo appeared to treat the public well. All the while, he was allegedly stalking and raping and members of the public.

james deangelo Exeter cop

In 1976, DeAngelo transferred to work as a police officer in Auburn. He worked in Auburn for three years until he was fired after he was caught shoplifting a hammer and a can of dog repellent from a drug store.

"Why is a law enforcement officer stealing dog repellent and a hammer?" asked Paul Holes, a recently-retired investigator with the Contra Costa County District Attorney's Office at Crimecon on Friday. "It speaks to a real deficit in him as a person."

Holes said when he was fired, authorities found lots of stolen property in DeAngelo's home, including power tools, still new in boxes.

"It goes to who he is, that he is getting off on getting away with stealing things. He just happened to get caught with the dog repellent and the hammer. He didn't want to bring more attention to himself, so he said okay [to the firing] and moved on."

Although there is no specific information available to the public which reveals that the Golden State Killer used a hammer in any of his killings, he was known to bludgeon victims to death with random objects.

Former Auburn Police Chief Nick Willick fired him but before that incident called him an average cop, according to CBS13 in Sacramento.

“If I remember correctly he didn’t even have a hearing,” Willick reflected about the shoplifting case. “I think he waived his hearing. He was prosecuted and we conducted our own investigation. And we terminated him based on the facts of the case.”

Not long after his arrest, the crime spree reappeared in Southern California, and many of the rapes accelerated to murder. It's not clear where DeAngelo lived during the Golden State Killer's most murderous years: from 1979 and the summer of 1981. That's when police think the killer murdered a dozen people.

In the late '80s, DeAngelo got hired at Save Mart, a grocery-store chain, as a mechanic. He remained employed there for nearly three decades.

A company spokeswoman said in a statement to the New York Daily News that, “None of his actions in the workplace would have led us to suspect any connection to crimes being attributed to him.”

DeAngelo went on to dodge further arrests until 2018. He was known as a suburban father and grandfather, who lived in a quiet neighborhood, Sacramento's Citrus Heights. His brother-in-law, James Huddle, told Oxygen.com that DeAngelo was a “good father.” One of his three daughters and a granddaughter were living with the suspect in his home until his arrest.

— Gina Pace contributed to this report.

[Photo: Santa Barbara County Sheriff's Department]