D.C. police are facing accusations of excessive force after a video surfaced appearing to show four officers trying to restrain a man on the ground before one officer punches the suspect in the head.

Police approached 23-year-old Samuel Cooper near the Brentwood Recreation Center on Saturday because they saw him drinking from a red plastic cup and holding a bottle of tequila, police said.

Cooper fled, police said. As he was running, he grabbed a handgun out of his pants and tossed it under a car, police said.

Eventually, police caught Cooper. Witness video shows four officers holding Cooper to the ground and struggling with him. Then, one officer punches Cooper in the head.

It's unclear if Cooper was handcuffed when he was punched. The person who filmed the video has not yet come forward.

Officers recovered the gun from under the car, which loaded. They also found a 17 round magazine on the scene. The gun was not registered, police say.

for

assault on a police officer while armed, carrying a pistol without a license, possession of unregistered ammunition, possession of an unregistered

firearm, possession of a large capacity ammunition feeding device, possession of an open container of alcohol, and drinking in public, and resisting

arrest.

Cooper was arrested on charges including assault on a police officer while armed, carrying a pistol without a license, possession of unregistered ammunition, possession of an unregistered firearm, possession of a large capacity ammunition feeding device, possession of an open container of alcohol drinking in public and resisting arrest.

D.C. police released a statement saying an investigation is ongoing: "As officers were affecting the arrest, the subject continued to actively resist. The incident has been turned over to our Internal Affairs Division to determine if the appropriate level of force was used."