The user is a zompire, a bizarre creature combining the traits of vampires and zombies.
They may have originally been vampires that feel prey to a zombifying virus or a mutating curse, or zomby infectees that were vampirized before the process was complete, probably as a desperate attempt to survive the infection.
The last (and worst) possibility would be an engineered hybrid virus combining traits of zombies and vampires, a terrible bioweapon of mass destruction, as zompires are much more powerful and intelligent than zombies, while sharing their ferocious voracity and exponential numbers.
Nonetheless, their vampiric and zomby cells are locked in an endless inner fight, forever healing and roting at the same time. While zompires make perfect bio-weapons, their entire existence is thus little more than a living hell.