The preliminary cause of death for Shelby County Coroner Brad Phegley is drowning, Shelby County Deputy Chief Richard Largen said.
Officials are doing research to see if Phegley had a medical emergency before his death, Largen said.
The Shelby County Sheriff's Office received a call on Friday at 2:49 p.m. that a man was floating in Lake Mattoon, officials said.
The caller was the victim's waterfoul hunting partner, responders said.
The caller found him near their decoys in front of their shoreline waterfowl blind, officers said.
The IDNR Conservation Police, Shelby County Sheriff's Office, Illinois State Police and Moultrie County Coroner are working to investigate the case.