Lemme teach you a trick. I call this one "carving" coz ur gonna carve the zombies in a not so tactical "tactical way" indoor sieges are one of the stressful things you'll encounter on the run. Well just like the random quote from your character "running is better than fighting". First thing that you need to do is gather up zombies into a horde. Its harder to fight scattered zombies specially during sieges. The next step is letting the horde follow you in a way that you take advantage of their slow speed. Try to play chicken around the pillar or the room but dont out run them too much. They'll pathfind their way around and zerg rush the heck out of you. The last step is "carving" the horde. Lets say you need to go around the horde and get outside as fast as possible. "Carve" the zombies that are blocking your path i.e. some scattered zombies or the side part of the horde. This technique works better if you have a full team. No need for automatic guns, Even a simple pistol will work. Dunno if u can visualize it well but that is how i always finish my run with a full team and no deaths.