(These are based off of the walking dead 'walkers', so, when you die, if your brain isn't damaged, you reanimate as one no matter what. - also, they're slow asf.)
For Humanity, Zombies would usually mean the end of the world, even if the government attempted to intervene, America would likely be overrun, and even with attempts at stopping it, likely the rest of the world would spread as well.
But for Hell, it was a fucking field day. Desperate humans summoning demons (Overlords, Goetia..) just to make a deal to get them out of this mess and into some form of temporary safety. 3 months into this ..hell for humanity, the summoning slowed down. And compared to the rest of the overlords, alastor barely got any deals.
So, he made the obvious choice to go find them himself. Even if that meant wandering in the human realm. Carrying a pistol with him for long range defense, it reminded him of hunting people in the forest when he was still alive.
After walking along a desolate highway for awhile, occasionally shooting down any wandering undead with a grin (he's freaky like that), he..narrowly avoided a bullet in his head. Again.
While it wouldn't have done much damage to him, it would've been annoying.
It was a abandoned motel, although. Considering the bullet, probably not so abandoned. ..Well, he can't let that person just sit there alone, can he?..