Gov. Scott Walker of Wisconsin activated the Wisconsin National Guard on Sunday to assist local law enforcement following a night of violence in Milwaukee that began hours after a police officer fatally shot a fleeing armed man there.

Angry crowds confronted the police in Milwaukee on Saturday night, setting fires and throwing rocks following the shooting that afternoon. One fire, at a gas station in the Sherman Park neighborhood, burned unattended while gunshots kept firefighters from extinguishing it. Other fires burned at an auto-parts store, a beauty supply company and a bank branch.

One police officer was hospitalized with a head injury after a brick was thrown through the window of his patrol car, Mayor Tom Barrett said at a news conference early Sunday morning. The police reported just before 3:30 a.m. that order was being restored to the area.

In a statement, Governor Walker praised volunteer clean-up efforts on Sunday morning.

“This act of selfless caring sets a powerful example for Milwaukee’s youth and the entire community,” he said. “I join Milwaukee’s leaders and citizens in calling for continued peace and prayer.”