A black man has been shot dead by police in front of a child in the US state of Minnesota as protests continued over the police killing of a black man in Louisiana.
Philando Castile, 32, was shot in his car as he reached for his driving licence, his girlfriend said in a Facebook Live video taken during the aftermath.
Her child was in the car at the time.
It follows the death of Alton Sterling, who was shot dead by police during an incident in Baton Rouge on Tuesday.
Hundreds of people have protested for two nights over Mr Sterling's killing.
The deaths follow a long line of high-profile incidents involving African-Americans at the hands of the police, igniting a national debate about the lethal use of force.
The footage taken by Mr Castile's girlfriend in Falcon Heights, a suburb of St Paul, shows Mr Castile covered in blood next to her and a police officer outside the car pointing his gun at him.
Mr Castile had earlier told the officer that he was licensed to carry a concealed gun and had one in his possession, she said.
"You shot four bullets into him, sir. He was just getting his license and registration, sir," the woman, identified in local media reports as Diamond Reynolds, says.
Mr Castile's mother, Valerie Castile, told CNN that her son was just "black in the wrong place" and said there was "a silent war against African-American people".
Later on Thursday, an emotional Ms Reynolds said she had filmed the incident so "the world knows that these police are not here to protect and serve us, they are here to assassinate us".
Mr Castile worked as a cafeteria supervisor at a Montessori school. His cousin Antonio Johnson told the Star Tribune newspaper he was "immediately criminally profiled" because he was black.
As news of the latest shooting spread, about 200 people protested outside the St Paul home of Minnesota Governor Mark Dayton, who later requested a federal investigation into the shooting.
In a statement on Facebook, President Barack Obama said all Americans "should be deeply troubled" by the latest death and the shooting in Baton Rouge.
He said it was clear that they were not isolated incidents but "symptomatic of the broader challenges within our criminal justice system".
Black US tennis player Serena Williams, who is playing at the Wimbledon tournament, also expressed her dismay at news of Mr Castile's death, in a tweet.
In London I have to wake up to this. He was black. Shot 4 times? When will something be done- no REALLY be done?!?! pic.twitter.com/OaLn60G6nm— Serena Williams (@serenawilliams) July 7, 2016
Police said an investigation was under way and the officer involved had been put on leave.
Protests continue in Baton Rouge
In Baton Rouge, hundreds of people gathered for a second night of protests at the shop where Mr Sterling, 37, was killed on Tuesday.
Some demonstrators chanted "black lives matter" and called for justice.
A video emerged on Wednesday that showed the altercation between Mr Sterling and two police officers.
It appears to show Mr Sterling being held down and then shot several times, although some shots are heard when the camera moves away from the confrontation.
Seconds later, one of the officers is seen removing an object from the man's trousers as he lies on the ground with blood on his chest.
Police have said Mr Sterling was found to be armed. Officers were initially called because of a 911 report of a man brandishing a gun.
The footage was provided to the Daily Beast by the shop owner, Abdullah Muflahi, who said it proves the man was no threat to the officers when he was shot.
Mr Sterling, a father of five, died at the scene and hours later a video filmed by a bystander which showed his death was released.
The officers involved, Blane Salamoni and Howie Lake II, were put on administrative leave.
The US Department of Justice has launched a civil rights investigation and Louisiana Governor John Bel Edwards has appealed for calm.