Minnesota state officials have identified the two police officers involved in the fatal shooting of Philando Castile, who was shot during a traffic stop Wednesday while his girlfriend, seated in the passenger seat, streamed video of the bloody aftermath on Facebook.

Officer Jeronimo Yanez and Officer Joseph Kauser have both been with the St. Anthony Police Department for four years and are both on administrative leave, according to a statement issued by the Department of Public Safety.

"Officer Yanez approached the vehicle from the driver's side and Officer Kauser from the passenger side. At one point during the interaction, Officer Yanez discharged his weapon, striking Castile multiple times. No one else was injured. A gun was recovered at the scene," the statement reads.

Castile's death was second fatal police shooting of a black man in as many days and has sparked outrage in the United States.

Relatives and friends identified the man shot by police in St. Paul, Minn., as 32-year-old Philando Castile. (Philando Castile/Facebook) The killing of Castile, 32, prompted Minnesota Gov. Mark Dayton to call on the U.S. Department of Justice to begin an investigation.

"Nobody should be shot and killed in Minnesota for a tail light being out of function," Dayton told reporters Thursday. "Would this have happened if the driver and the passengers were white? I don't think it would have."

The Minnesota Bureau of Criminal Apprehension has opened its own investigation.

Castile's death occurred within a day of the shooting of 37-year-old Alton Sterling in Baton Rouge, La. Sterling was killed during an altercation with two white police officers. Graphic video of that incident also triggered protests.

Wednesday's shooting happened in the St. Paul suburb of Falcon Heights, a community of 5,000 that is also home to Minnesota's annual state fair and part of the massive University of Minnesota campus.

Castile's girlfriend, Diamond Reynolds, broadcast the aftermath of the shooting from inside the car using Facebook Live.

WARNING GRAPHIC CONTENT: Unverified Facebook Live video of shooting aftermath

Shows man bleeding in car with woman and child and officer at window 9:50

As word of the incident spread, scores of people gathered at the scene of the shooting. The protesters then moved on to the governor's mansion in nearby St. Paul, where around 200 people chanted and demanded action. "No justice, no sleep," the protesters chanted. "Mark Dayton, do you care?"

Speaking outside the mansion, Reynolds said she chose to stream the video to prevent potential tampering with evidence.

"I didn't do it for pity. I didn't do it for fame," she said, surrounded by supporters and the media.

"I did it so the world knows these police are not here to protect and serve us. They're here to assassinate us. They're here to kill us, because we are black," she said, before collapsing into the arms of a man, identified by someone in the crowd as a pastor.

A crowd gathers at the scene of the police shooting in Falcon Heights, Minn. (Leila Navidi/Star Tribune via Associated Press)

Reynolds said the officer told them both to raise their hands and then asked for Castile's identification. She said he told the officer he was armed, reached for his wallet, and was shot.

"Either you want my hands in the air or you want my information," she said.

Relatives were outraged that Castile was not tended to after he was shot. Reynolds said it took about 15 minutes for paramedics to arrive.

WARNING: this video contains graphic language

Dramatic video

In the dramatic video posted late Wednesday night, Reynolds is shown inside the car, seated in the passenger seat next to Castile, who is slumped in the driver's seat. His white T-shirt is heavily stained with what appears to be blood.

Outside his window, a pair of hands is holding a handgun, aimed inside the car.

"We got pulled over for a busted tail light," she says to the camera, going on to describe the sequence of events with what appears to be surprising calm.

The officer tells her to keep her hands visible, intermittently swearing.

"I will, sir," she says.

"I told him not to reach for it. I told him to get his hand out," the man shouts.

"You shot four bullets into him, sir," she responds. "He was just getting his licence and registration, sir."

The video continues for nine minutes, during which she is detained and apparently placed in a police car, along with a little girl she identifies as her daughter.

"The police just shot my boyfriend for no apparent reason," she says.

Investigators work at the scene of the police shooting in Falcon Heights, Minn. (Leila Navidi/Star Tribune via Associated Press)

Police said in a statement that a handgun was recovered from the scene. They did not release any details about the officer who fired the shots except to say he had been placed on paid administrative leave.

Interim police Chief Jon Mangseth said he was aware of the Facebook video but did not comment on it.

The image in the video appears to be flipped — with the car's steering wheel on the wrong side. According to CNN, this is because the footage was shot with the phone's front-facing camera.

Castile's mother said she had instructed her son to always "comply" if he was ever stopped by law enforcement.

Castile told CNN her son was just "black in the wrong place" and that he was a victim of "a silent war against African-American people."

Mother and uncle of 32-year-old black man shot dead by police in Minnesota appear on U.S. network TV Thursday morning 1:10

'A gentle spirit'

Castile had worked for the St. Paul school district since he was 19. A principal described him as "a warm person and a gentle spirit" who loved his job and never missed work.

Katherine Holmquist-Burks hired Castile three years ago to supervise the cafeteria at J.J. Hill Montessori, a St. Paul magnet school with 530 students and 85 staff members.

"He stood out because he was happy, friendly and related to people well," she said.

After learning of his death, she went to the governor's mansion, in the same neighbourhood as the school, to take part in a vigil. "I want his name respected," she said.

Minnesota court records online show Castile had some misdemeanour violations, mainly related to driving.