The Glynn County Coroner's Office said Thursday county Commissioner Tom Sublett drowned Tuesday morning.
An autopsy also found a gunshot wound to the head, and Sublett's hands were tied with plastic zip ties, the Coroner's Office said.
When Sublett fell into the river off a dock at St. Simons Boating and Fishing Club, he was alive, even though he'd been shot in the head, officials said. The 52-year-old's body was found before dawn between a boat and a dock.
No weapon has been found, despite an extensive search by divers, including from the Navy.
The manner of death still has not been determined to be a homicide or suicide.
The case is now in the hands of the Georgia Bureau of Investigation.