The family filed a missing persons report then and has since been waiting on answers for more than a decade.
Fullerton police have now uncovered incriminating DNA evidence and filed a murder charge in the 30-year-old cold case.
David Richard Campbell, who is currently serving two sentences in state prison for the 1981 murders of William Raber and John Fischer, was recently re-interviewed and reportedly confessed to killing Marshall. The suspect, who was friends with the victim, told authorities where had disposed of his friend's remains.
During the later investigation, detectives learned hikers had located a skull in the San Bernardino Mountains in 1985. The San Bernardino County Sheriff's Department begun an extensive murder investigation then but was never able to positively identify the skull.
Following the new evidence, investigators were able to confirm the bullets in the skull matched those from the suspect's previous murder cases.
Using modern research techniques, Campbell's confession and a DNA sample from Marshall's brother, investigators were able to identify the skull found as that of the former Fullerton resident.
"This has been a long journey for the family of Bart Marshall", said Fullerton Police Chief Dan Hughes. "Just not knowing what happened to your brother or family member for over 30 years was agony for them. Even though Campbell is in custody for life, the family deserves closure and justice for their tragic loss. I am pleased our investigators were able to provide closure for them and hold the person responsible for this senseless murder accountable", said Hughes.
Fullerton police presented the case to the Orange County District Attorney's Office Wednesday and filed homicide charges with special circumstances against Campbell. He is eligible for the death penalty.