Three main theories exist about what happened to Martin.[16]
The first is that he became lost and perished from exposure or some other cause, likely during the first night. This is the most probable theory according to park officials.[1]
The second is that he was attacked by a hungry bear (or, less likely, a feral pig) and carried off.[5]
The third is that he was abducted and taken out of the park by something or someone. His father was a proponent of the third theory.[17] On the afternoon that Martin disappeared, tourist Harold Key and his family, heard an "enormous, sickening scream" and shortly thereafter witnessed a man covered in hair seemingly hiding and carrying something on his shoulder. Park Rangers and the Federal Bureau of Investigation concluded that there was insufficient evidence to link the sighting to Martin's disappearance, particularly given that Key's sighting was approximately five miles away from where Martin disappeared. The sighting occurred a little while after Dennis went missing. The family also said the person of the woods had something slumped over its shoulder, and the highly visible red color matching the shirt of Martin the day he went missing.[16][5]