It's not the guns that choose to kill people, it's the people that choose to kill people. Nobody here (besides any jokers/trolls) disagrees about that. The real issue is one of people, not guns. You are not going to solve the issues of school attacks or crime by taking away guns. There will always be other methods for people to get and build their own functioning firearms.
Let me give an example:
People can go to home depot and buy various parts such as air compressors, springs and PVC pipe to assemble homemade pneumatic firearms capable of firing solid and deadly projectiles such as marbles, batteries, and even real bullets at speeds comparable to that of a gun.
An example of such a weapon here.Don't even get me started on how easy it is to make homemade bombs.