Aron Ralson is an Amerian mountain climber,and he is used to taking risks.On April 26,2003, Aron's arm was caught under a 360-kilo rock that fell on him when he was climbing by himself in the mountains. He could not free his arm. Five days later when his water ran out, In order to save his own life, he had to cut off his righ arm with his knife. Then he bandaged himself and climbed down the mountain for help.