WGN News spoke with Laurie Walker and her daughter, Grace, who were inside the park when the shooting incident occurred.
Walker said they were waiting in line for an attraction in the southwest area of the park around 7.50pm when she noticed people running in a panic.
"There is an active shooter, get down, get down," Walker recalled someone shouting. "We didn't know what was going on, so we got down."
Walker and her daughter climbed over two fences to get "out of plain view sight," where she could call her husband. After hiding out for a short while, Walker says she was able to leave the park.
Gurnee is in Lake County, about 32km north of Highland Park, where seven people died in a mass shooting during a July Fourth parade