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Two times in two days last week, he leaped into a 4,000-foot canyon deep inside Navajo territory, gliding in his wingsuit before pulling the cord on his chute. On Friday, he jumped a third time, following his two friends to the bottom of the canyon.

‘‘The last time I saw Dave alive he was relaxed and smiling, sat in the sun,’’ Ralph Greenaway, one of base jumpers with him, said in a blog post. ‘‘His intention was to gear up and jump after watching our flight.’’

But the doctor failed to meet them at the bottom of the jump. They later spotted his bright wingsuit on a ledge overlooking the confluence of the Colorado and the Little Colorado Rivers.

‘‘A rescue helicopter … located Dave’s body and confirmed he had died from massive injuries resulting from impacting rocks at high speed. Death is believed to have been instantaneous,’’ Mr. Greenaway said.

‘‘Sitting around our camp fire the night before Dave’s death he could not have been happier. He talked about his life, his work and the days jumping with equal enthusiasm. It is my belief that he loved where he was in life.’’

Dr. Stather was 41 years old. He was unmarried, a clinical assistant professor who specialized in respirology — the study of lung diseases. Dr. MacEachern said Dr. Stather was particularly adept at bronchoscopy, the use of a camera at the end of a long tube, to perform internal examinations of the lungs.

“It took him over 10 years to get the training needed to do that job, so he’s not someone who can be easily replaced. He went at things full tilt, just like his hobbies,” said Dr. Paul MacEachern, who had known Dr. Stather for several years.