I think the bigger problem here is going to be 3D printed guns, which some dipshit already made available. He's one of those ultra-gun loving morons though and believes anybody and everybody should have access to lethal weapons.
In the not so distant future, 3D printers will cost about $150 and you can download blueprints for a gun, and poof. you have a deadly weapon. It's only going to get worse. You have to draw a line somewhere to prevent shit like this from happening, because not everyone should be allowed to have a weapon that can kill 40 people in less than 2 minutes. I say, if you can mow down 40 people in a building, none of them standing a remote chance of fighting back, that the line should be drawn well before that. It's not necessary and never will be.