A 29-year-old corrections officers says he was severely beaten by six Boston police officers after he attempted to film them with a cell phone camera during a traffic accident investigation.

Michael O’Brian, who works for the Middlesex Sheriff’s Office, said he suffered a brain injury during the March 16 beating.

He filed a federal lawsuit today, according to the Boston Herald.

O’Brien claims Officer David Williams led an attack on him after responding to a car accident involving O’Brien’s friend. O’Brien claims Williams threw him to the ground and choked him after another officer grabbed his cell phone while he filmed police.

O’Brien was charged with disorderly conduct, resisting arrest and assault and battery on one of the officers.