I envision the mallers have been kicking in doors and straight up snatching people from their homes. A vast majority of the population are normal cubicle workers and sofa quarterbacks. They have a simple home or an apartment to board up and stay in. They won't be able to keep out a determined armed group.
I'm trying to wrap my head around the thought of people still in a mall while all this is breaking out, but I think you mentioned that people would have run there for protection.. right?