Mountaineer cuts off his own arm with a pocket knife.. As reported in the Rocky Mountain News. Aron Ralston, after being trapped with his arm under a rock for five days, decided that if he did not get free he would die. Using his pocketknife, he amputated his arm below the elbow, put on a tourniquet and administered first- aid. He then rigged anchors and fixed a rope to rappel to the floor of Blue John Canyon. [kuro5hin.org]