Here in the UK, as you'll know, there is no common culture of gun-carrying. We don't own them, we don't feel we need them, we hardly even think about them.
Guns are legally held by certain parties for sport or work but a farmer, for example, who can own a shotgun can't buy an assault rifle.
We're not perfect - Britain has had American-style spree killings over the years. Many Brits could probably recall and name them, they're so unusual.
But we certainly don't expect to hear about them happening most weeks or have to design schools with 'anti-shooter' features.
Seriously, not being flippant here: how do Americans deal with the knowledge that any stranger they encounter might have a gun and shoot them?