A man found dead from cyanide poisoning inside a Boise, Idaho, church in 1982 has finally been identified, resolving a decades-old mystery that investigators had examined for possible connections to other poisoning deaths, inclu ding the Chicago Tylenol murders.Ada County officials announced Wednesday that the man, known for more than 40 years as the Unknown Wanderer, was Dr. Mathew Francis Betkouski.Investigators say Betkouski has been ruled out as a suspect in other homicides the Unknown Wanderer had previously been linked to. They are now asking the public for information that could help answer more questions about his death and his movements in late 1982.Betkouski lived in several states, including California and Florida. Investigators are particularly interested in any suspicious cyanide deaths during that period and information about where Betkouski was in the months leading up to his death.Photos from 2024 showed Betkouski was in Chicago in December 1981, but investigators have not been able to place him there in 1982. He is not being named as a suspect in the 1982 Tylenol poisonings.Ada County Sheriff Matt Clifford said former Boise police detective Frank Richardson laid important groundwork in the original investigation.[He] did everything right with the case he had in 1982, Clifford said. A lot of what we're able to tell you today is because of that foundation.Ada County Cold Case Detective Tim Cooper said the sheriffs office became involved in the case in 2018 after a member of Sacred Heart Catholic Church contacted investigators.The case was reopened in 2019, and investigators cross-referenced it with more than 17,000 missing-person records. But Betkouski had never been reported missing, officials said.Investigators eventually found a key that had been carried by the man, which Cooper said had an etching that led investigators to Mills Court, a street in Jacksonville, Florida.The sheriffs office was able to obtain property deeds connected to the location. Investigators also found a death record from 1989 tied to the location. They contacted a surviving family member, who told investigators that his brother had gone missing in 1982 and was later declared dead in absentia.A DNA sample was collected from the family member, a man living in Los Angeles. Cooper said the DNA showed that the Los Angeles man and the Unknown Wanderer had the same father, which allowed investigators to officially identify the wanderer as Dr. Mathew Francis Betkouski.This was an example of good citizens and experts coming together, Cooper said.If you have information that could help investigators, contact the Ada County Sheriffs Office at [email protected] said that a new Unsolved Mysteries documentary, Unmasking the Tylenol Killer, featuring this investigation is set to premiere in October.This story was originally published by the Scripps News Group station in Boise, Idaho. ...read more read less