He's a Werewolf

Werewolves, the most common of the were creatures, beings cursed by the animal transforming lycanthrope curse. There are several different ways a werewolf may come to be, being bitten by a werewolf creates what is called a thrall, a sort of werewolf who is nothing more then a beast during the full moon, but completely obedient to the one that turned him or her, they are servants and slaves of werewolf society. Then there are the pureblooded werewolves, werewolves born from werewolves, even those bitten, have control of the curse and are considered to be high ranking members of lycan society. Then there is the First Born werewolves, extinct since millenniums, they are the first were creatures, born of the curse which they spread out like an affliction, if a first born werewolf was to be found it could be a danger as it has no min, not even that of an animal, it is insane with blood lust and the desire to kill.