If you must shop the malls and big box stores, take it upon yourself to avoid entry into these places while pick-ups or deliveries are blocking or reasonably close to store entrances. Terrorists are not going to drive up in a vehicle with terrorist logo on the exterior of the vehicle. They're going to be inconspicuous and catch people totally unaware. The tiniest of cars can be loaded with explosives as well as large pickup trucks, SUVs and commercial vehicles.
THAT'S RIGHT and so can bicycles and motorcylces be packed, too, sorry to say.
The key is to look for any vehicle "improperly parked or parked in locations not normally associated with deliveries."
I'll add this:
Also watch for vehicles abandoned on a street or in a parking lot and vehicles left running with no one in them.
All good ideas to remember when shopping at malls.
One thing I would add is to always know where exits are. Most smaller stores between the big department stores have back doors for delivery which would be a good escape route if needed.