Three people were shot around closing time Sunday in a Six Flags Great America parking lot in Gurnee, Ill., authorities said.
Several ambulances rushed to the scene as video posted on social media showed people hunkered down and trying to hide, CBS News reported.
People at the park ran as gunshots rang out, though at least some did not recognize them at first.
“I thought there were fireworks right away,” witness Charlie Donda told CBS News. “Then we saw hundreds of people running. It was pretty scary, but we are safe.”
The shooting occurred in Lake County, the same jurisdiction as the July 4 massacre at the Highland Park holiday parade.