Why we have Sandy Hook and Aurora and Tucson and VATech, etc., etc.

Have a listen to this... Lt. Col. David Grossman. Psychologist.

Excellent.

https://www.youtube.com/watch?v=FX4k96Z4U5E

I've read a couple of his books, On Killing and On Combat. Both are good reads for anyone that has been in combat, might see combat, LEOs and also those that carry a gun for self defense.