The second fatal police shooting of a black man in two days has sparked outrage in the US, this one particularly chilling because the victim's girlfriend posted live video on the internet of the bloody scene minutes afterwards.
The killing of Philando Castile, 32, who was shot by a police officer after a traffic stop yesterday evening, prompted Minnesota Governor Mark Dayton to order a state investigation.
"Would this have happened if the driver and the passengers were white? I don't think it would have," Mr Dayton said.
"So I'm forced to confront that this kind of racism exists, and it's incumbent upon all of us to vow and ensure that it doesn't happen and doesn't continue to happen."
Mr Castile's death occurred within a day of the shooting of 37-year-old Alton Sterling in Baton Rouge, Louisiana.
Mr Sterling was killed during an altercation with two white police officers. Graphic video of that incident triggered protests and an outcry on social media.
Mr Dayton called for the US Department of Justice to open its own investigation, but the department said it would assist the state investigation as necessary.
The department has opened an investigation into the Baton Rouge shooting.
Mr Castile's girlfriend, Diamond Reynolds, videotaped the minutes immediately following his shooting and posted it on Facebook Live.
Mr Castile, who was driving, was shot with Ms Reynolds and her four-year-old daughter in the car.
Speaking at a NATO summit in Poland, President Barack Obama said these shootings are not isolated incidents and are symptomatic of a broader set of racial disparities that exist in the US criminal justice system.
"All of us as Americans should be troubled by these shootings because these are not isolated incidents," he said, adding that all Americans should be troubled by the shootings.
In an earlier Facebook post, President Obama said he and wife Michelle shared the "anger, frustration and grief" many Americans feel.
The use of force by police against African-Americans in cities from Ferguson, Missouri, to Baltimore and New York has sparked periodic and sometimes violent protests in the past two years, and has spawned a movement called Black Lives Matter.
Anger has intensified when the officers involved in such incidents have been acquitted or not charged at all.
Ms Reynolds' video showed a police officer outside the car pointing a gun. Ms Reynolds described what was going on, sometimes speaking calmly to the police officer, sometimes with her voice rising as she feared Mr Castile was dying.
Ms Reynolds said Mr Castile was shot after police pulled their car over, citing a broken tail light.
"Nothing within his body language said 'Kill me, I want to be dead,'" she said.
Dozens of protesters gathered at the governor's mansion in St Paul, about 15km southeast of the scene of the incident, where the governor spoke at a news conference with Ms Reynolds and civil rights activists.
When Ms Reynolds spoke earlier in the day, people shouted "murder," and called for the arrest of the police officer involved.
Demonstrations over the deaths and that of other black men killed by police were planned in St Paul, New York, Chicago and several smaller cities this evening, according to organisers posting on social media.
Weekend protests as far away as London were being discussed on Twitter.
A statement on the website of the City of Falcon Heights, where the shooting occurred, said a Saint Anthony Village police officer discharged his gun during a traffic stop on Wednesday evening, and the unidentified driver later died at hospital from resulting injuries.
It said the officer involved had been placed on paid administrative leave, as is standard procedure for Falcon Heights, which is about 10km northeast of downtown Minneapolis.
The ethnicity of the police officer was not clear. Attempts to reach the police department for further comment were unsuccessful.
Minnesota officials declined in a press conference to identify the officer who shot Mr Castile, saying they were still interviewing him.
His identity would be released after the interview was completed, they said.
The city's website said the Saint Anthony Village police department was working with the Minnesota Bureau of Criminal Apprehension and other law enforcement agencies on an investigation.
The labour union that represents the officer who shot Mr Castile urged people to reserve judgement.
Ms Reynolds said police had not even tried to check if her boyfriend was alive after they shot him, and it had taken at least 15 minutes for paramedics to arrive. She said he was shot five times.
The video Reynolds posted to Facebook began with her in the passenger seat describing what had happened moments before.
A black man covered in blood sat in the driver's seat as a police officer pointed a gun into the vehicle.
She said her boyfriend had just been pulled over and explained he had a gun he was licensed to carry.
"He was trying to get out his ID and his wallet out of his pocket," Ms Reynolds said. "He let the officer know that he had a firearm and that he was reaching for his wallet, and the officer just shot him in his arm."
Police said a handgun was recovered at the scene.
