“When he made that right turn, that’s when he turned really dangerous,” Mr. Hickey said.
Angelito Tenorio, a candidate for state treasurer, had just finished marching in the parade and was circling back to Main Street when he saw the S.U.V. speeding along the route.
“All of a sudden I heard a loud bang,” said Mr. Tenorio, an alderman for nearby West Allis. “Then I heard deafening cries and screams. It was very gut-wrenching.”
He described a chaotic scene that left him stunned and shaking.
“People were running away, leaving their belongings behind, sobbing,” he said. “When the crowd cleared out, it looked like there were people on the ground who might have been struck by the vehicle.”
In a video posted on the city’s Facebook page, the S.U.V. can be seen speeding down the parade route and screams can be heard from those in the crowd. Then, seconds later, a police officer runs by, followed by a number of police vehicles as a group of children stops performing.
Peggy Tom, 58, said that after the car sped past her, she walked down the street searching for a friend, whom she later found out was injured.
There were “piles of instruments,” Ms. Tom said, “and shoes.”
Others walking through the chaotic scene, she added, were shouting the names of lost loved ones.
Don Paul Browne, a city alderman, was marching in the parade with the mayor but had already left and did not witness what happened. He said the city was celebrating its 125th anniversary.