One person is on life support after being shot during a second night of protests in Charlotte as North Carolina's governor declared a state of emergency.
The city said the gunshot was fired by one civilian at another, not by police.
An officer is said to have also been injured in the demonstration and Charlotte Police Chief Kerr Putney described the protest as "very aggressive".
"We're trying to disperse the crowd. We've been very patient, but now they've become very aggressive, throwing bottles and so forth, at my officers, so it's time for us now to restore order."
Police in the city have fired rubber bullets and tear gas on protesters in a bid to break up the demonstration.
North Carolina's National Guard and the state's Highway Patrol are also being deployed to help the police.
Those on the streets were also seen looting a convenience store after smashing its windows and a shop that sells athletic wear for fans of Charlotte's National Basketball League team, the Hornets.
Protesters first took to the city's streets on Tuesday after a police officer shot and killed a black man while they were looking for a different person earlier in the day.
Police said in a statement that Keith Lamont Scott got out of his car holding a firearm and posed an "imminent deadly threat".
Department spokesman Keith Trietley said that the 43-year-old got out of the car and back in, and when officers approached he got out of the car again with a gun, and at least one officer fired a weapon.
However, posts on social media reported that Scott was unarmed and disabled, and family members say he was holding a book and waiting to pick up his son from school.
Police said that a weapon had been recovered from Mr Lamont Scott, but did not comment on whether he was disabled or not.