Two young people riding in an autonomous vehicle were arrested in San Francisco after authorities allegedly found them in possession of an illegal “ghost gun.”

San Francisco Police Department did not identify the operator of the autonomous vehicle, but a Waymo spokesperson confirmed to The Times that the incident involved one of its cars.

The company alerted emergency services and “cooperated fully” with San Francisco police.

San Francisco police did not immediately respond to The Times’ request for comment Friday.

The hat-topped cars are now a fixture in San Francisco and Los Angeles, and even sparked a beeping backlash in Santa Monica.