“Then we heard a loud bang,” Mr Tenorio said. “And after that, we just heard deafening cries and screams from the crowd, from the people at the parade. And people started rushing, running away with tears in their eyes crying.”

Mr Tenorio said he saw about 10 people, children and adults, on the ground who appeared to have been hit by the vehicle.

“It just happened so fast,” he said. “It was pretty horrifying.”Corey Montiho, a Waukesha school district board member, said her daughter’s dance team was hit by the car.

“They were pom-poms and shoes and spilled hot chocolate everywhere. I had to go from one crumpled body to the other to find my daughter,” she told the Milwaukee Journal Sentinel.

Zach Heisler, who was at the parade, wrote on Twitter: “A car just broke through the police line, plowing through pedestrians and firing rounds out the window. Family and I are safe. Happened 20 feet in front of us.”