Metropolitan police said the body, which Carter told authorities about, was that of 47-year-old Helen Johnstone, Washington's WJLA-TV reported Thursday. Authorities it appeared she may have slipped and fell into the water while hiking.
Fire and Emergency Medical Services spokesman Scott Kane said Johnstone's body was discovered Wednesday while Carter was canoeing near Three Sisters Island.
"The canoer flagged down some boats and they called Fire and EMS," the District of Columbia official said.
Washington's WRC-TV said an autopsy will be conducted to determine the cause of death.