All officers of the police tactical intervention unit in the United States resigned, in protest at the suspension of two officers from work and the granting of unpaid leave after accusing them of brutality, according to US media reports.
In a video, which was widely circulated on Thursday, officers from the Buffalo Riot Department in Buffalo, New York, appeared to throw an elderly man on the floor.
The 75-year-old man was seriously injured and was taken to hospital.
According to reports, all 57 officers resigned from the riot squad to protest against the suspension of two officers.
The officers resigned from the emergency response unit, and not from their work in the police, according to the newspaper "Buffalo News".