This is why so many are already really late to the party. The groups/churchs around here are known to all the other groups/churchs, an this is a none issue for us. However in places just 30-40 miles away this will be in the forefront an most of those seem to think they will recover our stores after local stocks run out. Most of them/that type are so fat an out of shape after a 3 mile walk down a paved road they well be laying there asking for help to get up off the ground. Their logic is buy an AK, dress like Rambo, an their flush. They have no clue about tactics, como, or any other finer points of survival. They types will re-supply the streets in more ways than one.You're bigger problem is vetting of unknowns, and not over / under reacting.
Our biggest threat is from Atlanta, an Birmingham, but we all have a plan in place to deal with that trash very quickly if need be. Sad thing is a few of our members live in those shit holes, but they will also be the trip wires. We have plans of getting them out in very unconventional ways if need be.
Your right (b)Not(/b) every one will be a threat, so body language skills, an gut/enter voice will rule the day.