A video surfaced Wednesday showing California deputies shoving a compliant man to the ground, resulting in a violent blow to his head against the asphalt, while pushing away the woman recording the arrest.

The disturbing scene is caught on a 1:32 second video posted below.

A San Mateo County sheriff’s spokesperson told PINAC Wednesday night that he was not familiar with the incident, but will investigate and get back to us on Thursday.

Mai, the woman who recorded the arrest, writes:

“This is the San Mateo Sheriffs Department arresting our friend who is seen in handcuffs getting placed in the car, another friend walks over to ask why he’s being placed under arrest, and I’m still video taping and I get pushed by an officer and as I regaining my balance, you see the friend not handcuffed getting knocked out by a police officer, they then try to grab his arm and get him up. He woke up at the hospital around 5am the next morning, incident happened around 11pm the day before.”

The video starts with an unidentified male deputy threatening a female citizen with arrest for recording the deputies arresting her friend.

“Film it from a safe area. Go over that way. Film it from a safe area,” the deputy tells her.

“I’m safe right here. There’s a bunch of cops right here. You make us safe, right?” she politely tells the deputy.

Instead of leaving the area, she walks around some patrol cars to get a better angle of the arrest.

“They didn’t read his Miranda Rights. They did not read his Miranda Rights. They are detaining him. This is the license plate number right here,” she told those watching the events unfold.

Mai captures the license plate 1430438 of the patrol car, then walks closer to where her friend is in the process of being handcuffed and frisked by two deputies.

As she moves closer, a deputy then tells her to back up, and pushes her away. The edge of the screen captures her friend “Ritchie” violently smacking the ground and remaining motionless.