Of course, there is no way to effectively harden "soft targets" where access to the public is involved. As for "closed" public areas like school's or churches, "think airports"..cannot and will not happen. Police are armed because "bad guys" break laws and will do harm. Sociopathic killers who PLAN. Only armed intervention by masses of civilains, teachers, CCR, etc. can reduce the risk. .The "Regime" is NOT interested!
During current Regime (11/2008-now), 65,000,000 NIC's (National Instant Background Checks) required for the retail purchase of a firearm have been conducted (can acquire multiple firearm per NIC ). ~66% of ALL new firearms sold ( hand & longarm) are semi-auto >.22 cal. The Regime will now "GO AFTER THEM NOW!"