@Gene Cash and his adolescent - authority made me rebel
Unless you go to school during a zombie apocalypse (not real either) then there really is not any good reason for killing your classmates or teachers.
What we have is an local overdose of insanity, the unfortunate thing is that since the majority of people in the US are irrational then after living there for any length of time you will tend to be infected and accept irrational behaviour and values as being sane.
Given that guns are for killing and handguns/automatic rifles are designed for killing people, if you think killing people is acceptable then live in the US but also recognise that your acceptance includes other people's right to kill you and the ones you love.
There have been attempts in the past to change the US and rethink the idea that killing people is cool or necessary however these have been overwhelmingly rejected by the majority of the voters.
So if you do not like killing or your loved ones been killed then as a minority in the US the only option left to you is to move to somewhere else where your desires are in the majority and the minority who have US values can be safely locked up so they harm no one. Star spangled straightjacket optional