At least 20 people were shot, one fatally, early Sunday during a gathering in a parking lot in suburban Chicago, authorities said.

TV news video showed the strip mall lot filled with debris and police tape in Willowbrook, about 20 miles (32.1 kilometers) southwest of Chicago.

“There were at least 20 individuals shot. One victim is deceased,” said Eric Swanson, deputy chief at the DuPage County sheriff’s office. “The motive behind this incident is unclear. ... We transported numerous victims from the scene. Others just walked into area hospitals.”

The conditions of the wounded were not immediately available, Swanson told reporters.

“It was supposed to be like a Juneteenth celebration. We just started hearing shooting, so we dropped down until they stopped,” witness Markeshia Avery told WLS-TV.

Another witness, Craig Lotcie, said: “Everybody ran, and it was chaos.”

This is a developing story. Check back for updates.