A Washington State man has been formally charged in the slaying of a Canadian couple in 1987 after cutting-edge genealogy analysis and DNA evidence led to his arrest last month.

The Herald reports that prosecutors on Friday filed first-degree aggravated murder charges against 55-year-old William Talbott II.

Authorities say Talbott brutally killed 18-year-old Tanya Van Cuylenborg and 20-year-old Jay Cook, who disappeared while traveling to the Seattle area from their home in Saanich, British Colombia. At the time of the killings, Talbott was a delivery driver in Seattle who had a route near where the couple reportedly planned to visit.

A man gathering aluminum cans in late November 1987 discovered Van Cuylenborg’s body in a rural patch of woods. She was shot in the back of the head “execution style,” with the gun’s muzzle just inches from her head, according to a forensic analysis.

Evidence, which indicated that the teen had been raped, directly links Talbot to the slaying. Police found a spent shell casing by the body and zip ties used as bindings.

As for Cook, investigators believe Talbott strangled and beat him with rocks. His body was discovered near a bridge and zip ties also were located in the vicinity.

“From all available information, these acts of violence were as random as they were savage,” Craig Matheson, Snohomish County chief criminal deputy prosecutor, wrote in court documents.

The slayings went unsolved for more than three decades until a genealogist and scientists developed a “family tree” of Talbott using crime scene evidence and data that his cousins had submitted to public genealogy websites.

That examination identified Talbott, who most recently was living near the Sea-Tac International Airport and was working as a trucker, according to the newspaper.

Law enforcement kept Talbott under surveillance until they got a break in early May, when a cup fell out of his truck. Investigators swabbed the cup for DNA and it matched the crime scene evidence.

He was arrested days later and just weeks after authorities in California had used a similar tactic to capture the suspected Golden State Killer.

After Talbott’s arrest, a former roommate of his told police that he remembered seeing a van similar to one described as possibly linked to the killer at Talbott’s parents’ house, where Talbott had lived for a time when he lost his job in 1987.

If convicted, Talbott could serve life in prison.

[Feature Photo: Tanya Van Cuylenborg; Jay Cook/Handout]