VACAVILLE, Calif. (AP) — A California police department is investigating the violent arrest last week of an autistic teenager by an officer who responded to a stabbing report.

A door video camera captured images of the teen thrown to the ground and punched in the face April 21 in Vacaville, near San Francisco.

Police in a Facebook statement say that concerns about the arrest are justified.

The teen's father tells CBS13 his son was being picked on and got a metal object to defend himself in an altercation that was broken up before the officer arrived.

Police say a preliminary review indicates the arresting officer was unaware the suspect had special needs.