Exactly. Our infrastructure is so vulnerable, that I can think of multiple ways to disrupt daily routine and kill multiple people even without a gun, let alone

Exactly. Our infrastructure is so vulnerable, that I can think of multiple ways to disrupt daily routine and kill multiple people even without a gun, let alone suicide bombing -- dismantle/block the rails, drop an obstacle on a busy highway, poison the drinking water, cut electric wires open, sabotage industrial/power plants, set buildings on fire etc. heck, even shouting out loud "he's got a gun, run!!" in a crowded space could result in multiple injuries/deaths. If there were so many determined terrorists on our soil as various governments and agencies want us to believe, they would cause a significant damage, not just stage occasional attacks that are statistically insignificant. The smallest dog barks the loudest.