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JEFFERSON COUNTY, Colo. (KDVR) — A 76-year-old Conifer man is in custody at the Jefferson County Jail after his arrest for a 1978 murder.

Detectives believe Mark Personette murdered 15-year-old Marissa Rolf Harvey in San Francisco 43 years ago. Her case went cold, but it was reopened last year. Detectives linked Personette to the crime through advanced forensic science.

He’s lived in Conifer for years, and neighbors are shocked.

 “It’s crazy what you don’t know about people,” said Avery Aubin who lives across the street. 

He never expected anything like this but says Personette had some odd behaviors.

“He was always a little off,” Aubin said. “He would always walk down the road backward and just really weird stuff.”

Neighbor Ralph Bradt agreed with Aubin’s assessment. 

“He was friendly enough, just a little out there,” Bradt said. “He pretty much kept to himself, kind of you know, the crazy guy next door.”

San Francisco Police have released mug shots of Personette taken over the decades. They say it’s possible there are other victims, and they are urging law enforcement agencies across the country to take another look at their cold cases.