It's understandable that everyone is upset about what was used to commit the cowardly massacre, however you can't blame the tool, if people want to do a mass murder they're going to do it, there's a little thing called the black market where you can literally get any weapon you want, this maniac could've easily gotten a light machine gun or a couple of fragmentation grenades. Point is, you can't ban things from criminals, the best course of action is to improve security.