Francesco Dellamorte is clearly a domain lord within the Land of the Mists, stuck here for an unknown transgression. (There are all kinds of domains, nothing says one cannot be based on modern Earth.) Francesco is cursed with pursuing a woman who always escape his grasp, but come back as another person once he believes she's lost forever — not unlike Strahd von Zarovich.
He can kill whoever he wants because of his domain lord powers, even though he has no awareness of them. The dead coming back as zombies is just a natural property of the domain itself.
And when he tries to escape with Gnaghi, he naturally bumps into the domain's border, which is why the road abruptly ends up and only mists can be seen beyond.
Seriously, that was my immediate conclusion on seeing the movie ages ago.
