Protests have erupted in Minneapolis over the death of an unarmed black man who was filmed crying out for help and saying, "I can't breathe" as a white police officer pinned him down.
The arrest of George Floyd, a 47-year-old bouncer, on Monday night was filmed by a bystander, and showed a police officer pressing his knee into Mr Floyd's neck until he stopped moving.
Four officers have been fired over the incident, an unusually swift move by the Minneapolis police chief, but it has not quelled the wave of anger in Minnesota's largest city.
Thousands of protesters on Tuesday night gathered at the site of Mr Floyd's arrest, marching more than three kilometres to the local police station, and damaging the building's windows and vehicles.
Riot police eventually attempted to disperse the crowds with tear gas and projectiles.
Tense skirmishes between protesters and officers stretched late into the evening.
Mr Floyd's sister, Bridgett, said the officers involved in her brother's death should be charged with murder because "that's exactly what they did".
The occurrence of yet another deadly encounter between police and an unarmed black man comes at a time when America's race relations are once more in the spotlight.
Viral footage leaked this month which showed the killing of Ahmaud Arbery, an unarmed black jogger in Georgia, provoked public outrage across the country and led to the intervention of the US Justice Department.
Minneapolis police said Mr Floyd matched the description of a suspect in a forgery case, and he resisted arrest when approached by officers.
But footage of the incident has drawn condemnation from high-profile figures across the US, including Joe Biden, the presumptive Democratic presidential candidate.
The video showed Mr Floyd pressed against the ground with an officer kneeling on his neck. Mr Floyd said: "Please, please, please, I can't breathe. Please, man."
The arrest drew the attention of several witnesses, who gathered at the scene and became frustrated with the police as they watched Mr Floyd in distress.
The man called for his mother and said: "My stomach hurts, my neck hurts, everything hurts... I can't breathe."
As bystanders shouted their concern, one officer said, "he's talking, so he's breathing".
One man yelled repeatedly: "He's not responsive right now!"
Two witnesses, including one woman who said she was a Minneapolis firefighter, shouted at the officers to check the man's pulse. "Check his pulse right now and tell me what it is!" she said.
Minutes passed and Mr Floyd became motionless under the officer's restraint. The officer did not remove his knee until the man was loaded on to a gurney by paramedics.
Mr Floyd was taken to hospital where he soon died, police said.
Mr Biden said the officers who were fired "must be held responsible for their egregious actions", saying Mr Floyd "deserved better and his family deserves justice".