In the Haitian tradition of the myth, a Bokor or witch uses necromancy to reanimate the corpse to do it's will. And in the original stories of Zombies, they never had an appetite for brains or human flesh; they were just simply doing whatever they were told to do, thus the actually meaning of the word Zombie (which means "enslaved spirit"). Also in Haitian tradition there is a realm in which Zombies are said to come from, called "the zombie astral".
Usually the case of these reanimated corpses was that a witch doctor or someone very knowledgeable would mix together different psychoactive drugs into a powder and would then slip it to an unsuspecting victim and this would put the vicitim in a death-like state, which would cause them to act like a Zombie.
Although, I do love the modernized take on what Zombies have become, I would definitely love to see the actual origins of the myth of the zombie displayed. As I've said for many of these blogs, I have so many ideas to work with for my own stories.