Hitoshi Ogi was tied last in a line of five Japanese climbers making their way down one of the world's most dangerous mountains when an avalanche struck.
The rope snapped and the four people in front of him were swept away, either buried under three feet of snow or pushed into one of the deep hidden crevasses that pock the western face of Alaska's Mount McKinley.
Ogi, 69, tumbled 60 feet (18 meters) into a shallow fault in the mountainside and climbed his way out. He later told park rangers he looked around but couldn't find any of his companions.
Fourteen hours after Thursday's accident, Ogi stumbled into base camp. He had only minor injuries.
US National Park Service said Saturday that the four are presumed dead by either snow burial or injuries suffered in the fall.
Ogi's survival came during the busiest season on Mount McKinley on its most well-traveled route. Search teams spent parts of Friday and Saturday looking for the other four climbers, all older than 50 and all members of the Miyagi Workers Alpine Federation in Miyagi, Japan.
Recent snow on the trail made the going hazardous, but the weather on Thursday was calm, said U.S. National Park Service spokeswoman Maureen McLaughlin.
"Where the avalanche occurred, the vast majority (of the new snow) was not on the main route," McLaughlin said. "A small sliver of it was, and that's what took them."
The West Buttress route snakes down the mountain from a 20,320 summit to base camp two-and-a-half miles below. About two-thirds of the way down is Motorcycle Hill, a windy ridge that serves as a convenient stop for climbers on their way up to grin and take pictures.
That's where the avalanche struck, taking 64-year-old Yoshiaki Kato, 50-year-old Masako Suda, 56-year-old Michiko Suzuki, and 63-year-old Tamao Suzuki.
McLaughlin called it "an unlucky, random event."
"Avalanches do occur in this vicinity, but it's not common, she said.
Snowfall and wind have impeded a search for the missing climbers.
The climbers were attempting the busiest route, West Buttress, during the height of mountaineering season. Climbers took the route on 92 percent of attempts on Mount McKinley in 2011.
The Park Service said in a news release Saturday that nearly 400 people were currently on the Alaska mountain.
Mount McKinley, also known as Denali, is North America's tallest peak. While not a particularly tall peak by global standards, its latitude makes for far thinner air than is found in mountains closer to the equator. That, combined with the weather and temperatures, makes it a particularly dangerous climb.
Four people died on the mountain in 2009 and again in 2010. At least five people died in 2011 on Mount McKinley.