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Man, 67, found dead at lake in Yellowstone; search on for half-brother, 74, a former Navy Seal

Driftwood along the shore of Shoshone Lake (NPS / Jacob W. Frank)

CASPER, Wyo. — Yellowstone National Park said in a press release Tuesday that search and rescue teams have located the body of Mark O’Neill, 67.

O’Neill’s body was discovered on Monday morning along the east shore of Shoshone Lake in the park.

Search and rescue efforts remain active for O’Neill’s half-brother Kim Crumbo, 74. Yellowstone says that a family member on Sunday reported the two as overdue from a four-night backcountry trip to Shoshone Lake.

Park crews located a vacant campsite with gear on the southside of the lake on Sunday along with a canoe, paddle, personal flotation device and other belongings on the east shore of the lake.

Efforts to locate Crumbo, a former Navy Seal, will continue Tuesday with 10 search and rescue crew members on foot. A Grand Teton National Park interagency ship and crew is also assisting in the search.

Yellowstone notes that both O’Neill and Crumbo formerly worked for the National Park Service. O’Neill was from Chimacum, Washington. Crumbo is from Ogden, Utah.

“This incident remains under investigation,” Yellowstone said. “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 is Yellowstone’s second largest lake and 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),” Yellowstone said. “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.”