While its truly a sympathetic sight to see families grieving over such a heinous & cowardly act, our systemic knee jerk reaction that we must do something, always seems to miss what is behind the cause or prompting of the act. People are killed in many ways, yet you never here the push to legislatively ban.....autos, knives, fists, etc. The movie Minority Report was pure science fiction.
There will never be a time where we can predict with any grain of certainty, when someone is about "to go crazy". Not to mention most acts come about from a slow boil, pushed by combination of both immoral instability and outside influences. Such folks are going to get whatever tool they desire to inflict their desired result. And the WORST thing we can do as a society, is to make it even harder for the law abiding to better defend themselves from such vitriolic hatred or mental disorder