Protests have erupted in Minneapolis after four police officers were fired over the death of a black man who was pinned down by a white officer, in a case that has drawn comparisons Eric Garner, the African American man who died in 2014 after being placed in a chokehold by police.
Footage of the arrest on Monday night showed the man pleading "please, I can't breathe" with the officer, who then kept his knee on the man's neck for several minutes after he stopped moving.
The man was identified as George Floyd by Ben Crump, a prominent civil rights and personal injury lawyer who said he had been hired by Mr Floyd's family.
"We all watched the horrific death of George Floyd on video as witnesses begged the police officer to take him into the police car and get off his neck," Mr Crump said. "This abusive, excessive and inhumane use of force cost the life of a man who was being detained by the police for questioning about a non-violent charge."
Protests broke out in the city on Tuesday night and police tried to disperse demonstrators campaigning for racial justice with tear gas and stun grenades.
The footage of the arrest drew condemnation from officials across Minnesota, including from Senator Amy Klobuchar, the former Democratic presidential candidate.
"Being black in America should not be a death sentence," said Minneapolis Mayor Jacob Frey, as he apologised to the black community.
"For five minutes, we watched a white officer press his knee into a black man's neck. Five minutes. When you hear someone calling for help, you're supposed to help. This officer failed in the most basic, human sense," Mr Frey said.
Minneapolis police said the man matched the description of a suspect in a forgery case and resisted arrest. The video shows an unidentified officer kneeling on his neck and ignoring his pleas. "Please, please, please, I can't breathe. Please, man," Mr Floyd is heard telling the officer.
Minutes pass and Mr Floyd man becomes motionless under the officer's restraint. The officer leaves his knee on his neck for several minutes more.
The arrest drew the attention of several witnesses who gathered at the scene and became increasingly frustrated with the police as they watched Mr Floyd plead. In the footage, one bystander yells at the officers to check Mr Floyd's pulse, another points out that his nose is bleeding.
Medaria Arradondo, the Minneapolis Police chief, said the police policy for placing a suspect under control will form part of its internal investigation. At a press conference on Tuesday Mr Arradondo said he had been "up all night" reviewing the case and had made the decision to fire the four police officers involved.
Mr Arradondo said that when he was appointed to lead the department, "I was very steadfast and strong on what our department vision, values and culture change would be moving forward. One of those pillars is sanctity of life," he said.
The incident has led many to recall the Eric Garner case, where a New York City policeman said he was using a legal manoeuvre to force Mr Garner to the ground because he had resisted arrest. Mr Garner too was filmed pleading and saying he could not breathe. Mr Garner's autopsy report said the "chokehold" used by the police officer contributed to his death.
The officers involved in Mr Garner's death were never indicted, sparking protests over racial injustice and police brutality around the US.
The FBI is now conducting a separate federal civil rights investigation into Monday night's incident at the request of Minneapolis Police.
The police department said it was called at around 8pm on Monday to investigate a report of a forgery at a business. Police officers found the unnamed man, believed to be in his 40s, matching the suspect's description in his car.
"He was ordered to step from his car. After he got out, he physically resisted officers," Minneapolis police spokesman John Elder said. "Officers were able to get the suspect into handcuffs and noted he appeared to be suffering medical distress."
Mr Floyd was taken by ambulance to a hospital, where he soon died, police said. His name and cause of death will be released by the medical examiner in due course.
Minnesota Bureau of Criminal Apprehension are reviewing the officers' body camera footage. The agency said the officers' names will be released after they have been interviewed.