Washington PC police chief Cathy Lanier created a wave in the self-defense community when she told Anderson Cooper that people caught in active shooter situations should shoot back if armed. The clip was repeated on 60 Minutes here. Cathy talked about the time it took police to arrive at Columbine in 1999 in Colorado, and said that police in Paris used an “old model” for intervening when they took 35 minutes to intervene in the Bataclan in Paris.
It isn’t hard to imagine that this could be taken as promotion of lawful gun ownership for self-defense by homeowners. But most of the issue would be that people are normally unarmed in public places, and not allowed to possess weapons. Some libertarians and conservatives have been making this argument ever since the 2012 incident in Colorado with James Holmes.
It's logical to extend this discussion to the proposition that self and familial or community defense should be a moral responsibility (it is such in Switzerland).