A patrol sergeant heard about 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, Washington Post reported.
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 people were confirmed dead, and four others were seriously injured.
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 that 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.
RHM/PR