Updated

The California Highway Patrol is investigating video of one of its officers straddling a woman lying on the ground and punching her in the head on a Los Angeles freeway.

CHP Assistant Chief Chris O'Quinn said at a news conference Friday that the officer was trying to restrain a woman who'd been walking on Interstate 10, endangering herself and people in traffic.

Passing Driver David Diaz recorded the Tuesday incident and provided it to local TV stations.

The officer is on administrative leave while the CHP investigates. He has not been identified.

O'Quinn says the woman, who would not give her name, was not injured and is undergoing psychiatric evaluation.