Fremont County Sheriff's Deputies say a medical condition caused an elderly man to drown near Island Park.
Deputies and an Island Park ambulance crew were dispatched to Henry's Fork just north of Last Chance around 9:20 a.m., Monday, for a report of a possible drowning.
Medical personnel attempted to perform CPR on the victim, Robert Pressley Evans, 70, of Killington, Vermont, but were unsuccessful.
Evans was pronounced dead at the scene.
Investigators believe Evans suffered a medical condition which caused him to drown in the river.