It seems like this happens every week these days. What I can't understand is why these folks don't go shoot some drug dealers or crooked CEOs on Wall Street and are always targeting schools, movie theaters, etc.
I have no real idea 'why schools' ..but a few hunches:
Logistics:
-Grouped people in easy to corner areas
-Predictable (traffic flow, time of events, etc).
-No concealed carry might bring a perceived higher chance of success. (not arguing for or against guns in schools, but, I doubt they miss thinking of this)
-Low security / no metal detectors / usually poor surveillance systems and physical security.
-You don't look suspicious carrying a large bag. Even oddball bags are fairly normal on campus (specialty tools, art projects, etc. in addition to the typical backpacks)
Mental for location:
-Similar age group and demographics (They identify with the students and, in hate of themselves, choose similar victims.)
-Promising young people (crush something beautiful)
-Draws media attention: makes for a bigger impact
Mental general thoughts:
-Anger is an emotion that implies that a person can do something about the situation, which might be "humanity is evil" or some other maladaptive schema.
-The drugs used to treat depression and anxiety can have paradoxical effects (hence they have suicide warnings, and 'contact your doctor if you have violent thoughts' etc). Not saying that antidepressants cause these things, only that there is a correlation. Adhoc, not sure.
Just one thing to note..these people aren't necessarily "insane." They DO know what they are doing, that's part of what makes this stuff so scary. Sometimes they think it has some purpose or meaning, but, I remember the one shooting the guy was just a sociopath and said he 'just wanted to kill people.' But, more often, they have some 'anger toward humanity' type of vibe.