I'd look to see if the Gravity Gun was in the room.
Yes: If the gravity gun is intact in the room I'd climb up onto the nears roof and look down upon the zombies. Gravity gun holding a saw blade I would go out on a zombie killing spree. Hopefully that will get Father Gregory's attention so then I'll have a veteran on my side. He might even get me a shotgun that I'll probably accidentally shoot so then I don't get the achievement for going through Ravenholm with only the gravity gun. That's how I always ruin it...
No: I would find something that can be used as an improvised weapon. Lead pipe, crowbar, nail board, I don't care. After getting a weapon I'd try to stealth out. I just really hope that the fast zombies don't have keen sense of smell or hearing.
I think my main goal would be to escape. If it was a real zombie apocalypse my goal would be to survive (obviously) but I would do so by setting up a base and staying not running away. "Hey zombies! It's my town and I'm not leaving!" I guess that means I'll be the Father Gregory of my town.