When you get down into the tunnels, use the crowbar on the zombies instead of your guns. When you reach the part in the tunnels when the bats fly at you, use your hand gun on them. After that, use a combination of your shotgun and hand gun on the zombies. If you can do this successfully, you can finally get out of the tunnels and out of the chapter. There will be more zombies outside the tunnels for awhile; be ready for them.

To kill the shambling zombies that cover their faces, use the shotgun. Fire a shot to their ankles to kill them. Note: This only work when they are standing fully upright.