In the afternoon hours on April 26, 2003, Aron Ralston was canyoneering alone through Bluejohn Canyon, in eastern Wayne County, Utah, just south of the Horseshoe Canyon unit of Canyonlands National Park. While he was descending the lower stretches of the slot canyon, a suspended boulder dislodged while he was climbing down from it. The boulder first smashed his left hand, and then crushed his right hand against the canyon wall. Ralston had not informed anyone of his hiking plans, nor did he have any way to call for help.
Assuming that he would die without intervention, he spent five days slowly sipping his small amount of remaining water, approximately 350 ml (12 imp fl oz), and slowly eating his small amount of food, two burritos, while repeatedly trying to extricate his arm. His efforts were futile as he was unable to free his arm from the 800 lb (360 kg) chockstone. After three days of trying to lift and break the boulder, the dehydrated and delirious Ralston prepared to amputate his trapped arm at a point on the mid-forearm in order to escape. After having experimented with tourniquets and having made exploratory superficial cuts to his forearm, he realized, on the fourth day, that in order to free his arm he would have to cut through the bones in it, but the tools available were insufficient to do so.
After running out of food and water on the fifth day, Ralston decided to drink his own urine. He carved his name, date of birth and presumed date of death into the sandstone canyon wall, and videotaped his last goodbyes to his family. He did not expect to survive the night, but as he attempted to stay warm he began hallucinating and had a vision of himself playing with a future child while missing part of his right arm. Ralston credited this as giving him the belief that he would live.
After waking at dawn the following day he discovered that his arm had begun to decompose due to the lack of circulation, and became desperate to tear it off.  Ralston then had an epiphany that he could break his radius and ulna bones using torque against his trapped arm. He did so, then amputated his forearm with his multi-tool, using the dull 2-inch (50 mm) knife and pliers for the tougher tendons. The painful process took an hour, during which time he used tubing from a CamelBak as a tourniquet, taking care to leave major arteries until last. The manufacturer of the multi-tool was never named, but Ralston said “it was not a Leatherman but what you’d get if you bought a $15 flashlight and got a free multi-use tool.”
After freeing himself, Ralston climbed out of the slot canyon in which he had been trapped, rappelled down a 65-foot (20 m) sheer wall, then hiked out of the canyon. He was 8 miles (13 km) from his vehicle, and had no phone. However, after 6 miles (9.7 km) of hiking, he encountered a family on vacation from the Netherlands; Eric and Monique Meijer and their son Andy, who gave him food and water and hurried to alert the authorities. Ralston had feared he would bleed to death; he had lost 40 pounds (18 kg), including 25% of his blood volume. Rescuers searching for Ralston, alerted by his family that he was missing, had narrowed the search down to Canyonlands and he was picked up by a helicopter in a wide area of the canyon. He was rescued approximately four hours after amputating his arm.
Ralston later said that if he had amputated his arm earlier, he would have bled to death before being found, while if he had not done it he would have been found dead in the slot canyon days later.
His severed hand and forearm were retrieved from under the boulder by park authorities. According to television presenter Tom Brokaw, it took 13 men, a winch and a hydraulic jack to move the boulder so that Ralston’s arm could be removed. His arm was then cremated and the ashes given to Ralston. He returned to the accident scene with Tom Brokaw and a camera crew six months later, on his 28th birthday, to film a Dateline NBC special about the accident in which he scattered the ashes of his arm there, where, he said, they belong.