Keith Johnson was watching a YouTube video in his West Side Cincinnati home when he learned about Flock Safety, a privately owned network collecting license plate data from cameras installed across the country. The video mentioned a community-run site called Have I Been Flocked, which lets people search their license plate to see if they’re in the database. Johnson ran his plates. His car was there, as was the reason police searched for it: "Terminated employee." Johnson had recently lost his job at a Jewish community center in Amberley Village. He wasn't accused of a crime and hadn't been back to the property. But after his termination, community center leaders told police they were concerned he might return. Officers ran a background check and searched Flock, finding Johnson’s car hadn't been seen in the village for at least a month. To police, the search was routine. “Anybody could be a potential threat,” Chief Richie Wallace said. “It’s just a matter of searching the database.”...