Buzzard is a character with old ties to The Priest and at the comics start is being kept as a torture victim in The Priests tower. Buzzard is a cursed reversed zombie, someone who is still alive but crave the meat of the dead, but like zombies can't be killed by simply destroying the brain.
His past is vague but he appears to have been a sheriff in a town which were attacked by The Priest and have nightmares about the inhabitants blaming him for not saving them.
According to The Priest himself when he turned the town into zombies Buzzard locked himself in his cabin instead of protecting them. Only later did Buzzard go after The Priest for revenge but end up as his captive until he is able to send a message to The Goon.