It has become almost mandatory in any
movie involving zombies or zombie-like creatures... the scene in
which one of the protagonists confronts a friend or family member who
isn't quite the same anymore. Can he perform his duty to
civilization by pulling the trigger, or will he end up like them? Is
it right to kill a loved one who has become one of the undead
(or an alien pod-person, or a plague-infected mutant, or whatever)?