Two Buffalo police officers were suspended without pay Thursday after a video showed authorities knocking down a 75-year-old man during a protest, Mayor Byron Brown said.

In a statement, Brown said the suspension came after the city’s police commissioner launched an investigation into the incident. Brown did not identify the officers.

Brown said he was “deeply disturbed” by the video, which was published by the local National Public Radio affiliate, WBFO.

The man, who has not been publicly identified, is in serious but stable condition at a local hospital, Brown said.

In the video, the man can be seen approaching a large group of officers in tactical gear and saying something. The officers yell for him to move back before one appears to push him.

The man stumbles backward and falls. Seconds later, a pool of blood can be seen near his head.

The incident occurred shortly after the city’s 8 p.m. curfew, NBC affiliate WGRZ reported.

A Buffalo Police Department spokesman didn’t immediately respond to a request for comment. WGRZ initially reported that the department said that the man, who has not been identified, was injured after he tripped and fell.