June 18 (UPI) — At least one person has died and 20 others were injured during a mass shooting after Juneteenth celebrations in Illinois, witnesses and officials said Sunday.

Witness Markeshia Avery told WLS-TV that she heard shots ring out around 12:30 a.m. early Sunday morning after the Juneteenth celebration in the suburban Chicago town of Willowbrook, leading her and others dropped to the floor.

“They just kept going. After that, we literally scattered away,” she said.

DuPage County Deputy Sheriff Eric Swanson told CNN that at least one person has died and 20 others were injured.

Joe Ostrander, battalion chief of the Tri-State Fire Protection District, said that ten patients were transported to local hospitals and that two remain in critical condition.

“We were all just out, and, next thing you know shots just kept going off; everybody ran, and it was chaos,” another witness told WLS-TV.

Law enforcement officials told CNN that the motive for the shooting remained unclear while witnesses told WLS-TV that the incident happened in a strip mall parking lot where the festivities were happening.