Randy is known as a daredevil among his friends. One day he decides to impress his friends by de-muzzling a neighbour's pitbull. He leaps over the fence, wrestles the dog down, and takes off the muzzle. The dog instantly attacks him and takes a big chunk of flesh out of Randy's face. Who is legally responsible for Randy's injuries - Randy or the dog's owner? What is the name of the doctrine that covers this?