An unarmed black man died in New York state after he was hooded by police and held face down to the road for two minutes, body camera footage shows.
Daniel Prude, 41, was suffering from mental health issues when police restrained him in March.
He died in hospital a week later. His story has only now been made public by his family, who held a news conference.
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Mr Prude's death took place two months before the killing of George Floyd sparked global outrage.
Mr Floyd died in May after a white policeman knelt on his neck for nearly eight minutes.
Tensions have risen again in recent weeks after black man Jacob Blake was shot seven times in the back and paralysed during an arrest in Kenosha, Wisconsin, on 23 August, sparking large protests in the city that have turned violent.
Democratic presidential nominee Joe Biden has called for charges against police involved in Mr Blake's shooting and that of Breonna Taylor, an African-American woman who was killed in her Louisville, Kentucky home during a drug raid in March.
"I think we should let the judicial system work its way," he told a news conference in Delaware. "I do think at a minimum, they need to be charged, the officers."
US Attorney General William Barr on Wednesday dismissed accusations that black and white Americans were treated differently due to police racism.
In an interview with CNN, he said it was very rare for an unarmed black person to be shot by white officers.
"I think the narrative that the police are in some epidemic of shooting unarmed black men is simply a false narrative," he said.
How did Daniel Prude die?
Mr Prude's brother, Joe, called police in Rochester, New York, on 23 March as his sibling was suffering from acute mental health problems.
"I placed a phone call for my brother to get help, not for my brother to get lynched," he told Wednesday's news conference.
A warehouse worker from Chicago and father of five, Daniel Prude was visiting his brother at the time of his death.
Police body camera footage obtained by the family through a public records request shows Mr Prude, who had been running naked through the streets in a light snow before police arrived, lying unarmed as officers restrain him on the ground.
The video shows that Mr Prude complied immediately when officers arrived on the scene and ordered him to lie on the ground and put his hands behind his back. He can be heard saying: "Sure thing, sure thing."
He becomes agitated, at times swearing at the officers who surround him and spitting, but he does not appear to offer any physical resistance, according to the footage.
Mr Prude told officers he was infected with coronavirus, and they placed a "spit hood" over his head. "Spit hoods" are mesh fabric hoods placed over the heads of suspects to protect officers from a detainee's saliva.
Critics who oppose their use say they are distressing and humiliating, can cause panic in the detained person, and make it harder to notice if a prisoner is having difficulty breathing.
One officer is seen pressing down with both hands on Mr Prude's head and saying: "Stop spitting."
After he stops writhing and goes quiet, one officer notes: "He feels pretty cold."
Medics try to revive him before he is carried into an ambulance. He was taken off life support a week later on 30 March.
The family's lawyer said the reason the case was not made public earlier was that it had taken "months" for police footage to be released.
In a statement, New York state's attorney general called the death a "tragedy" and said an investigation was under way. The officers involved have not been suspended.
According to a post-mortem examination report seen by the Rochester-based Democrat and Chronicle newspaper, Mr Prude's death was a homicide caused by "complications of asphyxia in the setting of physical restraint".
The report also listed PCP, a strong hallucinogenic drug, as a complication.
According to the newspaper, Rochester police used pepper spray and pepper balls against protesters on Wednesday outside the Public Safety Building.
