Jay Cook was running an errand for his dad when he disappeared. It was November of 1987, and Cook, 20, and his girlfriend Tanya Van Cuylenberg, 19, had traveled all the way from British Columbia to Seattle to pick up a part for a furnace. They took the ferry from Bremerton, crashed in their van downtown and were never seen alive again. Now, The Everett Herald

reports that homicide detectives have released never before seen letters that they hope might help in solving the 23-year-old cold case.The letters started showing up just a week after the couple’s bodies were found. Addressed to the kid’s parents, the letter writer expressed his hatred for Canadians and threatened to kill again. The first two were dated Dec. 3, 1987 and postmarked in Seattle. A dozen others followed about once a month for a year. They were postmarked from Seattle, Los Angeles, New York and Canada. The writer sent Hallmark greeting cards with pictures of teddy bears and kittens for Father’s Day, Mother’s Day and Christmas. Sometimes the cards were signed “Tanya” or “Jay.” He also sent letters to the Royal Canadian Mounted Police and a British Columbia newspaper.The suspect’s DNA — which indicates he’s a man — doesn’t match that found on other evidence, including Cook’s van which was recovered in Bellingham. Police think he may have been an accomplice. Or maybe just a kook trying to get some attention. The Everett HeraldOne of the letters sent to the parents of the victims more than 20 years ago.Either way, they’re pretty sure he’s Canadian — based on his use of colloquialisms like “hallelujah bloody Jesus” and “greetings and salutations” — and they want to talk to him. And because they haven’t received any hits in the criminal databases, they’re hoping he’ll come forward.Back to the murders: Van Cuylenberg was found first. Roughly a week after she disappeared, cops discovered her body in Skagit County. She’d been sexually assaulted and shot, her hands bound with zip ties. Cook was found two days later in Monroe. He’d been strangled.Police speculate that the killer didn’t know the couple. That he was a man who carried a kit with zip ties, a gun and gloves and picked his targets at random. They also believe he may be responsible for other rapes or murders.If you have any information, please call the sheriff’s tip line at 425-388-3845.