ST. PAUL, Minn. Amid protests and national outrage over the brutal police slaying of Philando Castile, Minnesota Gov. Mark Dayton (D) said Thursday he believed racism played a major role in the killing.

Would this have happened if ... the driver and those passengers in the car were white? Dayton asked. I dont think it wouldve.

A police officer shot Castile , 32, at point-blank range Wednesday during a traffic stop in the St. Paul suburb of Falcon Heights. Castiles girlfriend, Diamond Reynolds, recorded the aftermath in a graphic video she posted to Facebook . The video shows his final moments as she sits in the car next to him, with her young daughter in the back seat.

The Justice Department announced Wednesday it will monitor an ongoing state investigation into Castiles death. A DOJ spokesperson said the department is also prepared, if necessary, to conduct a separate investigation and consider the matter under federal law.

Thursday evening, protesters converged on the Minnesota governors mansion, just miles from where Castile was killed, to demand justice for his death.

Devina Moore said she saw the video of Castiles death and thought of his mother. I cant imagine getting that phone call, she told The Huffington Post, looking at her young son. Thats what brought me out.