U.S. climbers in Peru likely fell 1,000 feet

• The bodies of Ben Horne and Gil Weiss were discovered over the weekend
• Their equipment was strewn over a glacier
• Weiss "had the most optimistic view on practically everything," his sister remembers

(CNN) -- A large, hanging and then collapsing chunk of ice is likely the reason why two American climbers died in Peru, an investigator said Monday.

The bodies of Ben Horne and Gil Weiss were found two days earlier, a heartbreaking end to a high-tech search.

The men disappeared while attempting to scale the south face of Palcaraju Oeste, a 6,110-meter (20,000-foot) tall mountain located in Huaraz, a region popular with climbers.

Ted Alexander, who coordinated an investigation and effort to find the men, said Horne and Weiss made it to the summit and ran into trouble on their way down.

Evidence suggests that one of the men likely went to look over a serac -- a large block of ice -- to see if they could descend. Something gave out, causing the climber to fall some 65 feet, said Alexander. But because the men would have been tethered together, that first fall likely pulled the other man off the edge, which sent them both spiraling off a large cliff.

"Their equipment was strewn over the glacier. There was sign of great impact. (It) would lead us to believe that they did fall. My guess, looking at the photos and from talking to our guys out there that it was probably about a 1,000-foot fall," Alexander said.

Weiss, 29, was the founder of Beyond Adventure, a company consisting of professional guides, logistical experts and photographers. He posted June 11 on his Facebook page that he was leaving Boulder, Colorado, for Peru "for another season in the High Andes."

On July 10, Horne, 32, posted pictures and a chronicle of experiences in Peru on the climbing blog Pullharder.org.

"The Cordillera Blanca is world renowned for its high altitude mountaineering," he wrote. "But almost as awesome as the mountains themselves is the motley crew of international climbers who come to try their hand at getting high, on big peaks, cheap and fast."

Shay Har-Noy, who heads the technology company Tomnod that uses satellite imagery, said he enlisted the help of climbers and technology experts to find the pair using an application he built, with hundreds of people at one point poring through satellite images looking for signs of an avalanche. That information was then sent to search and rescue crews on the ground in Peru.

Horne and Weiss were extremely fit and experienced climbers, having practiced the sport for more than a decade, according to Har-Noy. Weiss had been to Peru several times before, though this was Horne's first such visit.

"Gil had the most optimistic view on practically everything," Gil's sister Galit Weiss told CNN. "I think it's really important to understand that you have to make the most of what you've got, and you've got to be grateful for everyone in your life."