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On August 2, 2008, eleven mountaineers from international expeditions died following an avalanche on the Himalayan mountain K2, the second-highest mountain on Earth. Three others were seriously injured. It was the worst accident in the history of K2.

My condolences to the families of the climbers and of course they were brave, most of them tried saving others when the serac fell.

The collapse of a large serac was responsible for causing the deaths of 11 climbers on the world's second highest mountain, K2
A serac (originally from Swiss French sérac, a type of crumbly white cheese) is a block or column of ice formed by intersecting crevasses on a glacier.
The Pakistani military started a rescue operation early on August 4, 2008, using two helicopters. They rescued two injured and frostbitten Dutch climbers from the base camp.Four climbers, including an Italian were making their own way down the mountain. The four were flown to Skardu for treatment.
Names of the climbers who were killed,
Dren Mandi?, Jehan Baig, Kyeong-Hyo Park, Hyo-Gyeong Kim, Dong-Jin Hwang, Rolf Bae, Jumic Bhote, Pasang Bhote, Hugues D’Aubarede, Gerard McDonnell.
Two Nepalese, Two pakistanis, three South koreans, one Irish , One french and One was from Norway.

Crevasses are known cause of deaths on K2 because of the hanging glacier.

Other website mentioned that this happened in the dead zone, above 8000M.

Full info: http://en.wikipedia.org/wiki/August_2008_K2_climbing_accident