It began innocuously enough.

A man started crossing a street, just as a vehicle drove through the intersection. As he finished crossing, another car went by in the opposite direction.

The man’s movements caught the attention of a Sacramento police officer who called him over.

“You’re jaywalking,” the officer said.

Less than a minute later, the encounter devolved into a chaotic and violent episode. Video recordings show the officer, who is white, throwing the man, who is black, to the ground and pinning him, before striking him in the face at least a dozen times.

“Oh my God!” screamed Naomi Montaie, who recorded a video of the episode and posted it on Facebook.

The encounter, which took place on Monday, is the latest in a series of incidents involving police use of force that have been captured on video and spread widely on social media. Such episodes have given rise to distrust between law enforcement and black and Hispanic communities, especially since the fatal shooting of an unarmed black teenager by a white police officer in Ferguson, Mo., in 2014.