Philando Castile
Philando Castile was shot and killed by a police officer after being asked for ID.Philando Castile/Facebook

Minnesota Governor Mark Dayton said popular elementary school worker Philando Castile who was shot dead by police as he reached for his driver's license would be alive today had he been white.

Castile, about to turn 33, was killed during a traffic stop apparently over a broken tail light in Falcon Heights, a Minneapolis suburb.

Castile's fiancée, Diamond Reynolds, who was in the car with her four-year-old daughter and recorded the aftermath of the shooting on steaming video, said her boyfriend was shot five times as he sat at the steering wheel reaching into his back pocket for his ID.

Governor Dayton called the shooting "appalling," and said race was clearly a factor.

"Would this have happened if those passengers, the driver were white?" he asked at a press conference, the Wall Street Journal reported. "I don't think it would have."

He added: "I can't say how shocked I am and deeply, deeply offended that this would happen to somebody in Minnesota. No one should be shot in Minnesota for a taillight being out of function. No one should be killed in Minnesota while seated in their car.

"I'm forced to confront and I think all Minnesotans are forced to confront that this kind of racism exists."

President Obama said he was "deeply troubled" by the shooting which is the the second controversial police killing of a black man this week. Alton Sterling was shot dead in Baton Rouge, Louisiana.

"We've seen such tragedies far too many times, and our hearts go out to the families and communities who've suffered such a painful loss," Obama said in a statement posted on Facebook.

"What's clear is that these fatal shootings are not isolated incidents," he added. "They are symptomatic of the broader challenges within our criminal justice system, the racial disparities that appear across the system year after year, and the resulting lack of trust that exists between law enforcement and too many of the communities they serve."

The US Justice Department is already investigating the Louisiana shooting. Federal officials are also now assessing the Minnesota incident.

Falcon Heights' St. Anthony Police Department hasn't released details of what led to the shooting nor said how many times Castile was shot. The officer who fired his weapon hasn't been identified, but he was reportedly placed on paid administrative leave.

"I told him not to reach for it; I told him to get his hand off it" says a nervous officer in Reynolds' video as he holds a gun on the wounded Castile.

"You told him to get his ID, sir, and his driver's license," Reynolds explains on the video. She also says on the cell-phone video that Castile had a "license to carry" a gun and informed the officer that he had a firearm.

She adds: "Please don't tell me he's dead. Please don't tell me my boyfriend just went like that."

According to Reynolds, two officers were involved in the traffic stop. One cop was on her side of the car, the other, a "very nervous" Asian-American, was on the driver's side.

Castile had no felony or violent criminal record, but he did have a history of traffic violations from speeding to driving without insurance.

Castile was beloved "Mr. Phil" to children in the JJ Montessori school in nearby St. Paul, where Castile was a cafeteria supervisor.

"We entrusted our children to him during the school day, and our children loved him," Donn O'Malley, chairman of the school's Parent Teacher Organization, told NBC News.

"When I saw the news this morning and told my children about it, they were sad, confused and immediately started sharing with me how great Phil was."

Protesters quickly gathered at the shooting scene and moved to the governor's mansion in St. Paul.