A helicopter crew searches Shoshone Lake last week for the missing Kim Crumbo.

Yellowstone National Park announced Friday that after five days of search and rescue efforts to find a man missing at Shoshone Lake, it was transitioning to a recovery operation.

The park spent most of last week searching for Kim Crumbo, 74, after he and his half-brother Mark O’Neill, 67, were reported overdue by a family member on Sept. 19 from their four-night backcountry canoe trip to Shoshone Lake. Search and rescue crews located O’Neill’s body along the east shore of the lake on Sept. 20.

Both O’Neill and Crumbo are park service retirees. Crumbo, a former Navy Seal, is from Ogden, Utah. O’Neill is from Chimacum, Wash.

“Today (Sept. 24), crews from the National Park Service’s Submerged Resources Center will begin using sonar equipment to detect clues in the water,” the park said in a news release. “Park search crews continue to search for Crumbo by foot and boat, with assistance from Grand Teton National Park’s interagency helicopter. Recovery efforts will continue for the next several days as conditions warrant.”

The park said the incident is still under investigation.

“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,” the park said.

On 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.

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