Given that malls and big box stores are pretty much stupidity magnets (i.e. lotsa preoccupied people meandering about not paying attention), they also attarct a lot of predatory opportunists, and as the economy gets worse, so will the number of preditors out 'hunting' in a target rich environment. If you aren't seriously watching your "6" these days, you're pretty likely to have an unpleasant encounter, especially arond places like WalMart that cater to the less affluent/financially stressed. Fact of life.
I think the OP did a great job, no harm, no foul. From my keyboard, I have little doubt that he read the situation right, and kudos to his wife, too. Pax vobiscum.
The Second Amendment IS homeland defense!