The National Park Service recently identified a hiker who died in the Grand Canyon last week as a beloved 74-year-old Washington state doctor.

Grand Canyon Regional Communications Center staff received a report on May 15 of an unresponsive hiker on the North Kaibab Trail, about half a mile below the North Kaibab Trailhead.

Dr. Dennis Smith, of Olympia, Washington, was attempting a rim-to-rim hike from the South Rim to the North Rim when authorities and friends said he collapsed on the trail.

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Though there is limited cell phone service in the canyon, the incident happened close enough to the top that they were able to call for a park service helicopter. Medics restarted his heart, but it later stopped again, and he was pronounced dead at the scene.

His cause of death is under investigation by the Coconino County Medical Examiner’s Office, according to the park service.

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Fellow doctor, Tom Helpenstell, who worked with Smith for more than 30 years, told Fox News Digital the pair ran across the canyon when it was hotter, and he believes it was a “freak” accident.

“I think it was 100 degrees or close to it, but he’s really good about hydrating,” Helpenstell said. “He’s always drinking fluids. … He’s way too smart to be pushing beyond his limits. I think this was just a freak thing.”

After doing a short stint in the Navy, Smith, a former family practice doctor, became an orthopedic surgeon. He then started his own practice, Olympia Orthopaedic Associates, where he met Helpenstell in 1994.

“We worked together in the same office and assisted each other every Tuesday in surgeries for 30 years,” Helpenstell said. “He and I have run across the Grand Canyon three times, doing Ultra Trail-type running. Probably two years ago, he decided not to do running [anymore], so he was hiking with a group out of Tucson, Arizona, where he spends the winters.”

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Before deciding not to keep running, the pair ran up Mount Whitney together, completed full Iron Man competitions and Olympic-distance triathlons together, and climbed Mount Rainier.

“He’s super active, super fit,” Helpenstell said. “This was not even a run, this was a hike. I don’t want to downplay it. Grand Canyon’s a big day, for sure, but this was completely out of the blue.”

In addition to Smith’s athletic feats, Helpenstell said he was highly respected in his community for his work in general orthopedics, where he did trauma, hip and knee replacements. 

“He would jump in and take care of anyone at any time. Really, really great,” Helpenstell said. “Within the surgeon community, we’re the carpenters. … Even when he retired from his regular work [in 2021], he stayed on and took call for us and stayed up at night doing cases. He kept his hand in it, until just about a year and a half or two ago. He was an amazing man.”

“He read like crazy,” Helpenstell said. “He was like an encyclopedia. We would always joke, we don’t need Google, we have Dennis. He was really into health and nutrition, and what diets are the right ones to take, and what supplements. I mean, the guy was crazy about staying healthy. He had switched to playing pickleball because he thought it would make his brain learn new things, which would keep him from getting Alzheimer’s or anything like that. He was more focused than anyone I know about staying healthy and living long, which makes this hard.”

Smith leaves behind his wife, Evelyn, who would have celebrated their 50th anniversary on Sunday, and four children. 

He also leaves behind numerous grandchildren who he enjoyed hiking and running with.

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The NPS urged all visitors to Grand Canyon National Park, particularly those planning to hike or backpack in the inner canyon, to prepare for extreme heat.

Park rangers strongly advise against hiking in the inner canyon during the hottest part of the day, between 10 a.m. and 4 p.m. Hikers and backpackers attempting rigorous distances, such as rim to rim, through the inner canyon, are encouraged to be self-reliant to prevent emergency situations for themselves and responders. 

“Be aware that efforts to assist hikers may be delayed due to limited staff, the number of rescue calls, and employee safety requirements,” according to the park service.