AAnyone who dies comes back as a zombie, unless his brain is destroyed. It doesn't matter if the dead person had suffered a gunshot wound, a car accident, a paper cut: anyone who dies with an intact brain will reanimate a short while later. The 'Dead' movies never explain why this is so--although the characters in the movies have their theories.. Theories from fans include: radiation from a crashed satellite, alien bacteria from a crashed satellite, a chemical spill, an airborne virus, and the judgment of God.