A cop in San Francisco recently encountered an unexpected dilemma when he stopped a car driving at night without headlights, only to discover there was no one inside.

The vehicle turned out to be a self-driving car, and the meeting between the police officer and the self-driving car was taken on film by a passerby and shared on social media.

The clip, showing bemused officers circling the vehicle and peering through its window for several minutes, has been shared so widely that Cruise, the company that owns the vehicle, reacted on Twitter to explain what had happened.

It said the self-driving car “yielded to the police vehicle, then pulled over to the nearest safe location for the traffic stop, as intended. An officer contacted Cruise personnel and no citation was issued.”

In the footage, as the police are inspecting the parked vehicle, someone can be heard exclaiming, “There’s no one in it, it’s crazy!”