FALCON HEIGHTS, Minn. — A Minnesota prosecutor said Friday he has asked for a “prompt and thorough investigation” following the police killing of a black motorist whose girlfriend streamed the shooting’s gruesome aftermath live on Facebook.

Ramsey County Prosecutor John Choi said the video is part of the investigation into Wednesday’s shooting of Philando Castile in suburban St. Paul.

The school cafeteria supervisor was shot “for no apparent reason” while reaching for his wallet during a traffic stop, after telling the officer he had a gun and a permit to carry it, his girlfriend said in the video.

Choi declined to provide details about the incident. Police also have refused to say what led up to the traffic stop, why Castile was pulled over or why the officer drew his gun. But the

The prosecutor said the shooting highlighted the need for better interactions between police and black residents.

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“We must do better in our state and in our nation to improve police-community interactions to ensure the safety of everyone in this country, but particularly the safety of African Americans, who disproportionately lose their lives as a result,” Choi said during a news conference Friday.

He also acknowledged the wide reach of the Facebook video, noting “what is depicted in the video, it just makes you sad to watch all of that unfold.”

His comments came a day after Minnesota Gov. Mark Dayton entered a reignited national debate over how law enforcement treats people of color, saying police likely wouldn’t have fired if Castile had been white.

“Would this have happened if those passengers would have been white? I don’t think it would have,” Dayton said to a crowd gathered outside his residence Thursday.