Updated at 10:35 p.m. ET
The mayor of Minneapolis says four Minneapolis Police Department officers involved in the death of a black man in police custody have been terminated. The FBI is investigating the incident.
After the firings were announced, a crowd several blocks long marched from the site of the killing to the city's Third Precinct police building, according to The Star Tribune.
The glass door to the precinct entrance was smashed to pieces during the demonstration.
"Shortly before 8 p.m. [CT], police clad in riot gear were firing tear gas and sandbags at the protesters, who were throwing water bottles at them in what appeared to be a standoff," the newspaper said.
A 10-minute video widely circulated on social media and referenced by Minneapolis Mayor Jacob Frey shows a police officer using his knee to pin the man's neck to the ground for multiple minutes.
The man has been identified as George Floyd by the mayor and by Benjamin Crump, a prominent civil rights attorney who says he has been retained by Floyd's family.
In the video, Floyd repeatedly cries out and says, "I cannot breathe," while the officer continues to push down on the man's neck with his knee.
Floyd appears to become unresponsive after he has been pinned to the ground for several minutes. Bystanders plead with police to check Floyd for a pulse.
"He's not even resisting arrest right now, bro," one person is heard telling police.
Eventually, police and first responders are shown moving the still-unresponsive, handcuffed man onto a stretcher.
Minnesota's governor, Tim Walz, wrote on Twitter that "the lack of humanity in this disturbing video is sickening." MPD spokesperson Garrett Parten declined to comment to NPR on the authenticity of the video.
The MPD said in a statement that an altercation occurred in South Minneapolis on Monday evening. It said officers responded to a report of forgery in progress. The police department said a suspect was sitting on top of his car and appeared to be under the influence when police ordered him to step away from the vehicle. According to the statement, he "physically resisted officers."
"Officers were able to get the suspect into handcuffs and noted he appeared to be suffering medical distress. Officers called for an ambulance," the department said. "He was transported to Hennepin County Medical Center by ambulance where he died a short time later."
Police said that no weapons were used by the officers or the man during the encounter.
The FBI and Minnesota's Bureau of Criminal Apprehension are now investigating the incident, which could include potential civil rights violations, Frey told reporters on Tuesday morning.
"I've been trying to find the words to describe what happened," Frey said. "All I can come back to is that he should not have died. What we saw was horrible — completely and utterly messed up. This man's life matters."
"Being black in America should not be a death sentence," Frey said. "For five minutes, we watched as a white officer pressed his knee to the neck of a black man. ... When you hear someone calling for help, you are supposed to help. This officer failed in the most basic human sense."
Walz, the governor, vowed to find answers and "seek justice," Minnesota Public Radio reported.
Frey and Minneapolis Police Chief Medaria Arradondo noted at the news conference that the officers involved were wearing body cameras.
"Our community continues to be traumatized again, and again and again," Minneapolis City Councilwoman Andrea Jenkins said in a statement to local TV station KARE. "We must demand answers."
Amnesty International USA called for the police officer involved to be held accountable for what happened, citing circumstances similar to those in the death of Eric Garner in 2014. Garner also famously said he couldn't breathe as he was being apprehended by police in New York.
"We are incensed that nearly six years after Eric Garner uttered 'I can't breathe' as he was killed by the New York Police Department, police officers still don't seem to have learned to listen to a person's call for help," Amnesty's Kristina Roth said in a release. "The police must be held accountable for this use of deadly force, that may also violate the department's own policy."
Nearly four years ago, another police department in the area faced criticism for an incident in which an officer killed black motorist Philando Castile.
NPR has reached out to Minnesota's Bureau of Criminal Apprehension and the FBI; neither responded immediately.