In the apartments there is a steel door you can't get in...

Get puked on by a Boomer, then run to that door and attack the zombies.

Then melee the door about ten times, then go outside and set a car alarm off.

Then run back to the door, kill all the zombies, turn your flash-light off and melee the door ten times.

Shoot it with a shotgun until the door is not there.

There is heaps of witches in this room!