I can only think of two reasons for the shooters. The most likely; gangstas and druggies who think they can claim NO as their hellish turf, strip it bare, rape and pillage and then just 'blend in' claiming to be suffering flood victims after stashing the loot.
Or two, the shooters are fifth columnists, Islamic or not, who enjoy seeing America suffer and total chaos, and they want to maximize the damage. And then 'blend in' with the refugees.
Thanks and I agree.