If I'm in the mall then the whole Hee-Haw gang is with me. (Lord knows I don't go there of my own volition. crazy) So removing them from the situation would be the first order of business. Escape if possible or find cover or concealment (in that order) if escape isn't possible. IMO rounding those in the immediate area up and moving into a store room, dock or any other space that offers a defensible position would be the most likely option.

Very sad situation. The families involved could surely use our prayers.
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"There is not a man of us who does not at times need a helping hand to be stretched out to him, and then shame upon him who will not stretch out the helping hand to his brother." -Theodore Roosevelt