A Georgia police officer is under investigation after authorities say he kicked a handcuffed man in the head.

Police in Gwinnett County, just outside Atlanta, said in a news release Thursday that the officer kicked the man after responding as backup to help a supervisor with a traffic stop in Lawrenceville around 4 p.m. Wednesday.

An ambulance then responded and treated the handcuffed man. Police say the officer's shift commander initiated an "immediate investigation." The officer was sent home on administrative leave and his department-issued gun was taken.

The incident was captured on cellphone video by a witness sitting in traffic. Police said the video is "very disturbing and speaks for itself." The officer's name was not immediately released.