The department has confirmed it is investigating the incident involving its officers making an arrest at the Glendale Galleria on Saturday.
In the video, four officers are trying to subdue a man on the floor of a Dick's Sporting Goods store. He is on his back and struggling as officers are on top of him. At one point, it appears at least three of the officers punch and kick him in the head several times.
The department says the incident happened when officers with the downtown unit - some of them in plainclothes - responded to a report of a theft from a business at the mall Saturday around 7:10 p.m.
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The officers encountered the suspect inside the Dick's Sporting Goods store. They tried to detain him and a struggle ensued that was at least partially captured on cellphone video.
The suspect was arrested for petty theft and resisting an officer by force, and the stolen merchandise was recovered.
Police say after seeing this video, an investigation was initiated into all actions by the officers, who have all been placed on administrative leave.
The department says appropriate actions will be taken following the investigation.
The department is looking for additional witnesses and video to the incident. Anyone with information is asked to call the department at (818)548-4911.