The Lake County Coroner's Office said authorities responded to the area of Illinois Beach State Park near Zion just after 4:30 p.m. Witnesses told Lake County sheriff's deputies that bystanders had pulled a man from the water near the rocks.
Investigators believe the man was seen jumping into Lake Michigan from the rocks for several minutes. At some point, witnesses observed him floating farther from shore.
Bystanders pulled the man from the water and brought him toward shore as deputies arrived. Deputies began CPR before the man was transported to Vista Medical Center East, where he was pronounced dead.
The man has been identified as 45-year-old Asdrubal Guifarro Munoz, of Waukegan. Autopsy results indicate that Munoz's death is consistent with drowning, with a possible medical/neurological event preceding the drowning, the coroner's office said.
The Illinois Department of Natural Resources Conservation Police and the Lake County Coroner's Office are investigating.