Grand Teton National Park interagency helicopter at the Shoshone Lake search and rescue operations. Photo: Brian Wick // NPS

MAMMOTH HOT SPRINGS, Wyo. — This afternoon, Yellowstone National Park officials announced that an autopsy has determined that Mark O’Neill, whose body was found on the shore on Shoshone Lake, died of hypothermia.

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

Search and recovery efforts continue at the lake to locate Crumbo. 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.

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.

If you have information that could help investigators piece together a timeline of events, or if you were in the Shoshone Lake area between Sept. 12-19, please contact us, if you have not already, at 307-344-2428 or

Buckrail @ Caroline

Caroline Chapman is a Community News Reporter. She enjoys reading non-fiction, skiing, hiking, and playing piano in her downtime. Her favorite aspect about living in Jackson is the genuine admiration that Wyomingites share for the land and the life that it sustains.