Leaders in Charlotte, North Carolina are calling for calm and dialogue after the fatal shooting of a black man by police led to a night of violent street protests that injured 16 officers.
The Charlotte violence unfolded as demonstrators in Tulsa, Oklahoma, called for the arrest of a police officer there who was seen in widely viewed videos shooting to death an unarmed black man who had his hands in clear view at the time.
The incidents are the latest to raise questions of racial bias in US law enforcement.
Criminal investigations have been opened in both cities for the shootings, and the US Justice Department has started a separate probe into the Oklahoma incident to see if officers' use of force amounted to a civil rights violation.
"Our top priority is for Charlotte to remain a safe community for everyone who lives and visits here," Mayor Jennifer Roberts said at a news conference on Wednesday as she called for patience with the investigation.
A Charlotte-Mecklenburg Police officer killed Keith Scott, 43, who had been seen entering a vehicle with a handgun, Chief Kerr Putney said at the same news conference. Mr Scott was surrounded by police and was shot after he exited the car and did not obey officers' instructions to drop his weapon, Chief Putney said.
"He stepped out, posing a threat to the officers, and Officer Brentley Vinson subsequently fired his weapon, striking the subject", Chief Putney said, adding that police acted heroically in trying to stem the protests that followed the shooting.
Mr Scott's family says he was reading in his car and was unarmed. Police said they recovered a gun they said Scott was holding.
Chief Putney said a handgun was seized. "I can also tell you we did not find a book," Chief Putney said. "We did find a weapon."
North Carolina allows for the open carry of handguns, including having a pistol in a vehicle.
One protester was arrested, and several were injured in demonstrations that blocked an interstate highway.
Protesters set fires and stoned police cars, he said. Police deployed gas to disperse the crowd.
More protests were expected on Wednesday, and Chief Putney said: "It is time to change the narrative".