I hope it's not too soon to talk about this, but I'm starting to see increasing mentions on the news of how much ammunition this psycho purchased online. A sudden nationwide ban on gun sales would not be feasible (yet), but I can definitely foresee legislators targeting online ammo sales. They will either want to ban online ammo sales outright or add layers of complexity to making purchases. And if they are not already tracking ammo sales nationwide, they soon will be.
Plus, recent history shows that politicians do not like the internet. Between SOPA, PIPA, ACTA and demanding taxes from online retailers, this would be just the latest step "forward" into the digital age for our dear leaders.
I hope I'm wrong... but I doubt it.