Report: Man Found Dead In Yellowstone Last Week Died Of Hypothermia; Brother Still Missing

A man found dead in Yellowstone National Park last week died of hypothermia, park officials said. His half-brother is still missing.

Ellen Fike

September 29, 20212 min read

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A man found dead in Yellowstone National Park last week died of hypothermia, according to park officials.

Mark O’Neill, 67, of Chimacum, Washington, was found dead on the east shore of Shoshone Lake in Yellowstone National Park on Sept. 20. An autopsy determined his cause of death was exposure, or hypothermia.

O’Neill and his brother, 74-year-old Kim Crumbo of Ogden, Utah, were reported overdue by a family member on Sept. 19 from a four-night backcountry trip to the lake.

Crumbo is still missing and search and rescue teams continue to search for his body, as park officials announced last week they expected to recover, not rescue, him.

Crews from the National Park Service’s Submerged Resources Center are using sonar equipment to detect clues in the water. Park crews continue to search for Crumbo by foot and boat, with assistance from Grand Teton National Park’s interagency helicopter and dog teams from Western Montana Search Dogs.

These recovery efforts will continue for the next several days as conditions warrant.

The incident remains under investigation. Officials are asking for the public’s help in putting together a timeline of events, so if anyone was in the Shoshone Lake area between Sept. 12-19, contact officials at 307-344-2428 or

Both O’Neill and Crumbo are National Park Service retirees, and Crumbo is a former U.S. Navy SEAL.

Shoshone Lake, the park’s second-largest, is located at the head of the Lewis River southwest of West Thumb. At 8,050 acres, its average year-round temperature is about 48 degrees. Survival time in the cold water is estimated to be only 20 to 30 minutes.

Editor’s note: Crumbo and O’Neill were previously reported to be half-brothers by park officials, but this was corrected on Wednesday to note they are brothers.

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Ellen Fike