A police officer who fatally shot an unarmed black motorist in Tulsa, Oklahoma, has been charged with manslaughter, a prosecutor has said.
Officer Betty Shelby shot and killed Terence Crutcher last week while he was standing next to his broken-down car.
In Charlotte, North Carolina, a curfew went into effect to prevent a third night of violence after a black man was shot dead by a black police officer.
Keith Lamont Scott's family deny police allegations that he was armed.
Demonstrators protesting against Mr Scott's death in Charlotte have defied the curfew - running from midnight to 06:00 (18:00-00:00 GMT), some remaining on the streets singing gospel songs.
According to Cpt Mike Campagna, officers have not enforced the curfew as protests were largely peaceful.
However Charlotte police reported two officers were injured on Thursday night.
Hundreds of National Guard troops have been deployed on the streets. Some demonstrators demanded to see footage of the shooting which was released to Mr Scott's family but has not been made public.
The family's lawyer said the footage was inconclusive. But they have demanded its release to the public, which police have so far refused.
Officials say Keith Lamont Scott refused to drop his gun but his family say he was unarmed and holding a book.
It has also emerged that one man injured in gunfire in Charlotte died from his wounds.
The police use of force against black men has for two years been the subject of protests across the US, and now it has also become an election issue.
Four days before the first presidential debate, Republican Donald Trump said the violence was largely due to drugs.
"If you're not aware, drugs are a very, very big factor in what you're watching on television at night," he said.
Democratic vice-presidential candidate Tim Kaine said the list of black men fatally shot by police had "grown too long" and the country needed to confront the issue of racial tensions.
Republican Congressman Robert Pittenger, of North Carolina, told the BBC the protesters hated white people because white people were successful, but he later apologised for his comments in an interview with CNN.
In the aftermath of the Tulsa shooting, Officer Shelby said Mr Crutcher had not followed her commands and she had opened fire when he began to reach into his car window.
Ms Shelby's lawyer, Scott Wood, has said she believed Mr Crutcher was under the influence of the synthetic drug PCP. A vial of the drug was found in the car.
His family have disputed Ms Shelby's claim, arguing that his window was closed at the time of the incident.
Police have said no gun was found on Mr Crutcher or inside his vehicle.
As well as being shot, Mr Crutcher was also struck with a stun gun by another officer.
His death sparked protests in Tulsa too but these have been peaceful.
Mr Kunzweiler said a warrant has been issued for Ms Shelby's arrest. She faces a minimum of four years in prison.
The US justice department has also opened a separate investigation to see if Mr Crutcher's civil rights were violated.