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New York City police officers were seen clashing with demonstrators in another night of mass gatherings Thursday in a city that has seen some of the worst violence since George Floyd protests began more than a week ago.

But it was a clash across the Empire State, in Buffalo, that was attracting attention on social media.

In a shocking video that went viral, Buffalo police were seen pushing an elderly man backward, causing him to slam his head against the ground and appearing to knock him unconscious.

WARNING: GRAPHIC VIDEO

"He's bleeding out his ear!" someone is heard saying on the video.

The 75-year-old man was reported to be in "stable but serious condition" in a hospital and two police officers were immediately suspended. In addition, the city's police commissioner announced the start of an internal affairs investigation.

New York Gov. Andrew Cuomo called in the incident "wholly unjustified and utterly disgraceful."

BUFFALO PROTESTER PUSHED TO GROUND, STARTS BLEEDING, VIDEO SHOWS; 2 COPS SUSPENDED: REPORTS

Downstate, in the nation's largest city, law enforcement officers were out in force as an evening curfew took effect, in an attempt to keep the peace and prevent violence that has marred otherwise peaceful demonstrations regarding Floyd, whose death while in police custody last month has ignited a firestorm of criticism of law enforcement agencies over police brutality.

All across New York City, large gatherings began, coinciding with an emotional memorial service for Floyd in Minneapolis, the city where he died May 25 after having a police officer's knee on his neck for nearly nine minutes.

New York has seen some of the worst violence since protests began more than a week ago. On Wednesday, a police officer was stabbed in the neck and two others were shot.

Thousands remained in the streets after the city's 8 p.m. curfew took effect Thursday, as well as large numbers of police officers. In the Bronx, officers were seen clashing and aggressively charging toward demonstrators in an apparent attempt to keep crowd control. Other videos appeared to show the NYPD arresting curfew violators en masse, threatening protesters with jail and wielding batons at them.

Many demonstrators have accused the department of aggressively enforcing the city's curfew and engaging in the same militaristic behavior they are protesting against.

WARNING: VIDEO BELOW CONTAINS PROFANITY

Hours earlier, a massive crowd packed the Brooklyn Bridge, prompting officials to shut down traffic into Manhattan temporarily. A gathering near Gracie Mansion, the residence of Mayor Bill de Blasio, cleared out just before the curfew began. One group headed south from the area clashed with police on the Upper East Side and arrests were made.

In Chicago, rapper Kanye West marched with Chicago Public Schools students to demand the school district end its $33 million contract with the Chicago Police Department.

In the St. Louis area, hundreds gathered to call for criminal justice reforms. The city has seen a fair share of violence in recent days, as four police officers have been shot and a retired police captain killed while trying to protect a pawn shop from looters this week.

Protesters in Washington D.C., soaked in the rain as National Guard soldiers waited out the downpour inside one of the White House office buildings.

Multiple cities across the country have imposed curfews in an attempt to prevent widespread rioting and looting that has mostly occurred after dark. Wednesday night saw a break in the chaos as most gatherings remained peaceful.

On Thursday, thousands in Southern California and Washington, D.C., held vigils in honor of Floyd, similar to events in other parts of the country.

In Los Angeles County, officials lifted a county-wide curfew order Thursday, though some cities have chosen to keep their orders in place out of precaution. Los Angeles Mayor Eric Garcetti announced he also lifted his curfew order.

Curfews have become a sticking point between protesters and authorities. The American Civil Liberties Union and Black Lives Matter L.A.filed a lawsuit against local officials and law enforcement leaders in Southern California this week over the "draconian" orders.

Monday marked a week since Floyd, a 46-year-old black man, died while in the custody of Minneapolis police officers. A video of a white officer pinning his knee on Floyd's neck for nearly nine minutes went viral and has prompted outrage around the world.

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The officers involved have since been fired and criminally charged.

Fox News' David Aaro contributed to this story.