Yellowstone National Park said in a statement Wednesday that an autopsy had been performed on Mark O’Neill, 67, whose body was found on the east shore of Shoshone Lake in the park on Monday, September 20.
The autopsy determined that O’Neill’s cause of death was exposure (hypothermia).
O’Neill, of Chimacum, Wash., Along with his brother, Kim Crumbo, 74, of Ogden, Utah, were reported late by a family member on Sunday, September 19, after their four-night trip to the backcountry at Shoshone Lake. .
Park crews found a vacant campground with equipment on the south shore of Shoshone Lake, as well as a canoe, paddle, personal flotation device and other personal effects on the east shore of the lake.
Search and recovery efforts continue at the lake to locate Crumbo. Teams at the National Park Service’s Submerged Resource Center use sonar equipment to detect clues in the water.
Park crews continue to search for Crumbo on foot and by boat, with assistance from the Grand Teton National Park interagency helicopter and Western Montana Search Dogs dog teams. These recovery efforts will continue over the next few days if conditions warrant.
O’Neill and Crumbo are both retirees from the National Park Service, and Crumbo is a former Navy SEAL.
Shoshone Lake, the second largest lake in the park, is located at the head of the Lewis River southwest of West Thumb. The year round average temperature of the lake is around 48 F (9 C). Survival time is estimated at only 20 to 30 minutes in water at this temperature.
If you have any information that would assist investigators in establishing a timeline of events, or if you were in the Shoshone Lake area between September 12 and 19, you are encouraged to contact Yellowstone officials at 307-344-2428 or at [email protected]
The press release also states: “This incident is still under investigation. While we cannot comment further on the details of this investigation, we will provide updates as appropriate.”
Park officials also noted that Crumbo and O’Neill are brothers, not half-brothers as they initially reported.