I've shared this before, but:
Unless you just started shooting in the years since the Great Panic of the Winter of '12-'13, there's no reason you shouldn't already be well-stocked on stuff, but if you aren't, Commander Zero's advice applies:
"This is *exactly* the sort of event that nudges The Powers That Be into doing stupid things like 1994 Assault Weapons Ban: The Next Generation. Even if it doesn’t, its going to push gun/mags/ammo price and availability into the red zone. So…if you still haven’t gotten around to buying everything that might not be available at a later date….this is your reminder that crap like this, as tragic as it is, will always be used to tie your hands further when it comes to buying those useful guns and accessories."