Azazel later uses his pact with Mary to enter their home in the pilot episode, and ultimately kills her. The second-season episode "All Hell Breaks Loose, Part One" reveals that she had witnessed the demon secretly feeding his blood to Sam. John investigated the incident and learned of the existence of the supernatural. His desire to find and kill Azazel led him to become a hunter of supernatural creatures. He took his sons with him during his travels, but often left them alone in motels for long periods of time during his hunts, leaving Dean with instructions to "shoot first and ask questions later" while watching over Sam.