In the fall of 1987, a young Canadian couple set off from their hometown of Saanich, British Columbia to run a few errands in Seattle. They never made it there; police found their bodies a few days later near Bellingham, Washington. Jay Cook had been beaten and strangled. His girlfriend, Tanya Van Cuylenborg, had been raped and shot in the head. For more than 30 years their families held out hope that police would one day find the killer.

That day was Friday, May 18, when the Snohomish County sheriff’s office announced it had finally arrested a suspect: 55-year-old William Earl Talbott II. Investigators found him the same way California police identified a suspect in the Golden State Killer case just a few weeks ago—by uploading DNA data from decades-old crime scene evidence to the public genealogy site GEDmatch. The difference this time was that GEDmatch knew about the investigation.

Earlier this month, the open-source database—which houses nearly a million voluntarily contributed genetic profiles—changed its terms of service to explicitly allow law enforcement to use it, either to identify the remains of a deceased individual or identify a perpetrator of a violent crime. It’s the first such site to formally open its data riches to the police, lending this new genetic sleuthing practice a growing sense of legitimacy. And investigators are wasting no time in taking advantage, which means these two arrests are probably just the beginning.

GEDmatch has long been a theoretical source of leads for the police, says CeCe Moore, a genetic genealogist who worked on the Snohomish case. Up until a few weeks ago, she had mostly helped adopted people find their biological parents and celebrities track down their ancestors on the PBS television series Finding Your Roots. She often relied on GEDmatch to reverse engineer someone’s family tree, and with her particular knack for finding people, she got regular requests from police departments to help them crack a case. But she never felt comfortable working with law enforcement while GEDmatch's users were unaware their data might be used that way.

Then came the Golden State Killer case. Unbeknownst to the small roster of volunteers who run GEDmatch, California investigators used the site to generate a list of people that eventually led them to Joseph James DeAngelo, who they arrested April 24. After that, things moved very quickly.

“I knew right away, when I read that first news story that the unnamed site was GEDmatch,” says Moore. She scanned the headlines and social media, expecting there to be a lot of blowback about privacy concerns. But soon, a more altruistic consensus began to emerge. “The feeling was that GEDmatch should be considered public data, like the phonebook, or Facebook,” she says. “There’s no genetic exceptionalism; any data people put in there can be used as a tool for the public good.”

So a few days later, Moore accepted an offer to work with Parabon NanoLabs, a forensic DNA technology firm in Virginia. The company is paying her to helm the its brand new genetic genealogy unit, which the company announced May 8. Her first case? The Washington double murder.

Parabon specializes in DNA phenotyping—predicting the physical appearance of people from unidentified DNA evidence. For the past year, the company had been working with detectives from Snohomish and Skagit Counties to produce facial composite images of the 1987 double murder suspect. It was a last-ditch effort to produce a meaningful lead, after DNA evidence collected during the investigation had failed to match any profiles in the genetic databases available to law enforcement. But no one had come forward with any possible suspects.