Investigators in Washington state last week made an arrest in a 31-year-old double homicide, tracking the suspect down using the same genealogy techniques used to capture the suspected Golden State Killer. William Earl Talbott II, 55, of the Seattle-Tacoma area, was booked Thursday with one count of first-degree murder in the November 1987 death of Tanya Van Cuylenborg, 18, of British Columbia, Snohomish County Sheriff’s Office officials said Friday in a news conference. Van Cuylenborg and her boyfriend, 20-year-old Jay Cook, vanished Nov. 18, 1987, on an overnight trip to Seattle to buy furnace parts for Cook’s family’s business. They were reported missing when they failed to return home. A man found Van Cuylenborg’s body Nov. 24 near Bellingham in Skagit County. She had been bound with plastic zip ties, sexually abused and shot in the head, the Toronto Star reported. Cook’s body was found two days later, battered and wrapped in a blue blanket that did not belong to the couple, about 75 miles away under a bridge near Monroe, which is in Snohomish County. Cook had been beaten and strangled. “It's been 31 years since this horrific crime took place,” Skagit County Sheriff Will Reichardt said Friday. “Today, we are one step closer for justice for Jay Cook and Tanya Van Cuylenborg.” Investigators from Skagit and Snohomish counties worked the three-decades-long case together. Talbott’s arrest comes just five weeks after Snohomish County Sheriff Ty Trenary released composite drawings of a possible suspect that were made using DNA believed to have been left behind by the killer. The images showed a white man with light hair and green or hazel eyes. The killer’s DNA, which was found at the scene of Van Cuylenborg’s slaying, was also uploaded to a genealogy website and used to create family trees with people who shared significant amounts of DNA with the unknown suspect, officials said. CeCe Moore, the genealogist who worked on the case, said Friday that she traced the suspected killer’s DNA to his great-grandparents, then used “reverse genealogy” to fill in the blanks on the branches. “This led me to two descendants of the great-grandparents of the original matches who married, thus tying the two families together,” Moore said. The couple had one son -- Talbott. Once Talbott was identified as a potential suspect, detectives obtained his DNA from a cup he used and threw out. Reverse genealogy made headlines around the world earlier this year when investigators looking for the Golden State Killer, a serial killer and rapist believed to be responsible for 12 homicides, more than 50 rapes and about 100 burglaries across California in the 1970s and 1980s, arrested Joseph James DeAngelo Jr., 72, after they said they matched his DNA to that of the killer. Trenary on Friday thanked the investigators who never gave up on solving the slayings of the young Canadian couple. “It’s a difficult thing for us, but candidly, this is what we do our job for,” Trenary said. Reichardt said it was the forensic work that detectives did in 1987, which preserved the DNA evidence, that ultimately led to Talbott’s arrest. “The next step is prosecution,” Reichardt said. Cook and Van Cuylenborg left their Saanich homes bound for Victoria, where they were planning to take the Port Angeles ferry to Seattle. The couple made the ferry and were spotted buying snacks along the way to Seattle in Hoodsport and Allyn, both located in Mason County, Washington, according to Snohomish County officials. They were last seen alive buying tickets for the 11:35 p.m. Bremerton-to-Seattle ferry the night they vanished. KIRO 7 News in Seattle reported that Van Cuylenborg was found six days later, partially clothed, in a ditch. Cook’s van was found the next day, locked and abandoned, in a Blue Diamond parking lot in Bellingham, located in Whatcom County. Cook’s body was found the day after the van. The victims’ families last month offered a $50,000 reward to anyone who could provide information before the end of the year that would lead to a positive match to the DNA in the case, KIRO reported. Members of the Cook and Van Cuylenborg families were at Friday’s news conference. They expressed a mix of emotions at the news of Talbott’s arrest. “Yesterday, the killer had his last sleep in his own bed, his last coffee break, his last day of freedom,' Cook’s sister, Laura Baanstra, said. “It’s hard to put into words the relief, joy and great sorrow this arrest brings.” “They were both gentle souls, caring and trusting kids, and they were betrayed,” Van Cuylenborg’s brother, John, said. “Hopefully, this is a start of some justice for them.” Talbott has not yet been charged with Cook’s slaying, but investigators continue to process evidence and interview witnesses related to that portion of the case. Detectives are asking anyone who knew Talbott or his activities in 1987 or 1988 to come forward. Talbott, who was 24 years old at the time of the slayings, was living with his parents in Woodinville, about seven miles from where Cook’s body was found. Detectives are hoping to find witnesses who saw Talbott with Cook’s van in November 1987 or with a 35mm Minolta camera that Van Cuylenborg had with her at the time she was slain. The camera’s lens was recovered in 1990 and traced to a pawn shop in Portland, Oregon, police officials said. The body of the camera remains missing. They are also looking for anyone who knows anything about the blanket Cook’s body was found wrapped in. Anyone with information related to the case should call the Snohomish County Sheriff’s Office tip line at 425-388-3845.