BUFFALO, N.Y. -- -- Prosecutors were investigating Friday after a video captured police in Buffalo shoving a 75-year-old man who then fell and cracked his head, a confrontation that resulted in the suspension of two officers.

Video from public radio station WBFO of Thursday night's encounter, which happened near the conclusion of protests over the death of George Floyd in Minnesota, quickly sparked public outrage and a protest by city police who felt the officers were being mistreated.

It shows a man identified as Martin Gugino approaching a line of helmeted officers holding batons as they clear demonstrators from Niagara Square around the time of an 8 p.m. curfew. Two officers push Gugino backward, and he hits his head on the pavement. Blood spills as officers walk past. One officer leans down to check on the injured man before he is urged along by another officer. Gugino and the officers all appear to be white, but details of their backgrounds were not released.

"Why? Why was that necessary? Where was the threat?" asked Gov. Andrew Cuomo at his daily briefing Friday. The governor said he spoke to Gugino, who had been hospitalized in serious condition. "It's just fundamentally offensive and frightening. How did we get to this place?"

The confrontation raised concerns about more possible flare-ups in Buffalo this weekend, especially after city officers resigned en masse from the police squad charged with crowd control. The resigning officers keep their jobs.

"Fifty-seven resigned in disgust because of the treatment of two of their members, who were simply executing orders," said John Evans, Police Benevolent Association president, according to WGRZ.

Buffalo Mayor Byron Brown said contingency plans are in place "ensure public safety." Additional state troopers will be in the city through the weekend to assist Buffalo police, according to a state police spokesman. And Brown said they are working with other agencies.

Protests are expected to continue nationwide over the death of Floyd -- a Black man who died after a white police officer pressed a knee on his neck for several minutes.

Gugino was hospitalized and was "alert and oriented," according to a Friday morning tweet by Erie County Executive Mark Poloncarz.

Poloncarz at a briefing later in the day wished Gugino a "speedy recovery" and said the encounter "created a black mark, a stain on the city of Buffalo."

The police commissioner suspended two police officers without pay, said Brown.

The district attorney's office "continues to investigate the incident," officials said in a news release, but the victim could not talk to investigators Thursday night.

Gugino is a retiree who lives by himself in the area, say friends who describe him as a veteran peace activist driven by his faith and a desire for social justice. He is involved with the Western New York Peace Center and Latin American Solidarity Committee, said Vicki Ross, the centre's executive director.

"I can assure you, Martin is a peaceable person," Ross said. "There is no way that he was doing anything to accost or hurt. He made a judgment to stay out after the curfew because he feels that our civil liberties are so in danger, which they most certainly are."

His Twitter timeline includes tweets and retweets supportive of progressive causes and critical of police. One tweet from Wednesday read: "The cops should not have clubs. And should not be in riot gear. The National Guard should arrest the police."

Ross said Gugino has been undergoing chemotherapy for cancer.

"It doesn't surprise me that Martin was standing there looking at these young cops in the eye," Mark Colville of the Amistad Catholic Worker said of his longtime friend. "It almost looked like he was reaching out to them, trying to shake their hand or say, `What's going on? Why are you doing this?"'

Buffalo police initially said in a statement that a person "was injured when he tripped & fell," WIVB-TV reported, but Capt. Jeff Rinaldo later told the TV station an internal investigation was opened.

"When I saw the video, certainly, it was incredibly distressing and very disappointing. You don't want to see anything like that," Brown, the mayor, told WIVB-TV on Friday.

The office of state Attorney General Letitia James tweeted that officials there were aware of the video. U.S. Sen. Charles Schumer called for an investigation, according to a statement reported by WIVB-TV.

"The casual cruelty demonstrated by Buffalo police officers tonight is gut-wrenching and unacceptable," John Curr, the Buffalo chapter director for the New York Civil Liberties Union, said in a statement, adding that it should be a "wake-up call" for city leaders to address police violence.

Warning: The video contains images some viewers may find disturbing.

Correction:

This story has been updated to correct that the source of the video was WBFO, not WFBO.