Allen Kenitzer, a spokesman with the Federal Aviation Administration, says the plane went down Monday evening and was destroyed by fire.
Rescuers reached the remote crash site Tuesday afternoon and recovered the bodies of the crew members, said Jeanne Stone-Hunter, spokeswoman for Civil Air Patrol's Wyoming Wing.
Hunter says the pilot of the Cessna 182R last made radio contact with another pilot in the area at about 4 p.m. Monday.
Authorities say 16-year-old Keith Bellack of Gillette, Wyoming, who had disappeared Sunday while fishing, was found alive about an hour later.
The three Civil Air Patrol members killed are identified by authorities as Lt. Col. James Henderson, 59, and his two passengers, Senior Member James Meyer, 53, and Capt. Patricia Larson, 52.
The Civil Air Patrol is a nonprofit U.S. Air Force auxiliary organization that performs 95 percent of the nation's inland search and rescue operations, according to its Web site. The group has about 56,000 members nationwide, including more than 250 in Wyoming, and also specializes in aerospace education.