The following is a release from Yellowstone National Park –

Park search and rescue crews located the body of Mark O’Neill along the east shore of Shoshone Lake in Yellowstone National Park Monday, Sept. 20.

O’Neill, 67, from Chimacum, Washington, and his half-brother, Kim Crumbo, 74, from Ogden, Utah, were reported overdue by a family member Sunday, Sept. 19 from their four-night backcountry trip to Shoshone Lake.

On Sunday, Sept. 19, park crews located a vacant campsite with gear on the south side of Shoshone Lake, as well as a canoe, paddle, PFD and other personal belongings on the east shore of the lake. Crews located the body of O’Neill along the east shore during the morning of Monday, Sept. 20.

Search and rescue efforts continue with 10 crew members on foot in the area Tuesday, Sept. 21 to locate Crumbo. Grand Teton National Park Interagency ship and crew are also assisting with air operations.

Both O’Neill and Crumbo are National Park Service (NPS) retirees, and Crumbo is a former Navy Seal.

This incident remains under investigation. While we cannot comment further about the specifics of this investigation, we will provide updates when appropriate to do so. We ask the public to maintain distance from any law enforcement personnel, equipment, vehicles and their related activity for the safety of the public in this remote area and to protect the integrity of our work.

Shoshone Lake, the park’s second-largest lake, is located at the head of the Lewis River southwest of West Thumb. At 8,050 acres (3,258 ha), its average year-round temperature is about 48 F (9 C). Survival time is estimated to be only 20 to 30 minutes in water of this temperature. Learn more about boating regulations and safety in the park.