JOLIET, Ill. (AP) — Two people were killed and more than a dozen were injured in an overnight shooting at a suburban Chicago Halloween party, authorities said Sunday.

A patrol sergeant heard roughly a dozen gunshots after 12:30 a.m. in Joliet, which is about 45 miles southwest of Chicago, according to the Will County Sheriff’s Office. The sergeant went to a home and found more than 100 people fleeing a party.

Additional officers arrived and found victims in the backyard and at nearby homes, and more shots were heard nearby, authorities said.

The Will County Sheriff’s Office said more than a dozen people were hospitalized. Two were confirmed dead and four others were seriously hurt.

Police estimated about 200 people attended a Halloween party at the home and the shooting occurred outside near a DJ booth set up in the backyard.

Authorities said it appeared the shooting happened from “an elevated position on a porch looking down over the crowd.”

Witnesses told police they believed there were two shooters.

Police did not release further details, including a motive.

“This investigation is in its early stages, and Will County Sheriff’s Office personnel are still on scene preserving the crime scene and collecting evidence,” the office said in a news release.