In 2003, he decided to climb the remote Blue John Canyon in Utah.He also works as a motivational speaker, helping disabled athletes and troubled teens.Meanwhile, Aaron's friends and family realized he was missing and notified authorities, who discovered that Aaron had used his credit card to purchase food items in Moab, Utah.While crossing a 3-foot-wide rift in the canyon, an 800-pound boulder moved and got his arm stuck between it and the canyon wall.He administered first aid to himself, then tied a rope to the rock and climbed down about 70 feet to the bottom of the canyon.Thanks to his prosthetic arm, Aaron is a better climber than he was before his accident.He tried with all his might to get free and used his small knife to try to free his arm, but to no avail.