So why is he invinsible?

If you mean invincibility it's because he was raised by a voodoo priest.

Damned good question, and the main reason I thought this movie was unengaging. Was he alive or dead? Dead, if we are to believe the scene where he is shot multiple times without even reacting, including twice in the head, and that he was reportedly cold to the touch. Alive, if we are to believe the pathologist who patched him up (of course, he might well have died from his injuries later, in his girlfriend's care).

If he was alive, however, how can one explain the scene where he is ice cold and shot numerous times in the torso and twice in the head? One can't, so dead it is. That's the only thing that fits, also when taking the ending into consideration. But the movie did a pretty poor job of explaining anything.