We are dealing with big generalizations here. In reality, this likely had zero to do with Trump, Obama, Bush, Clinton, or any other politician or political ideology. This was a fk'd up kid who, by some reports, was highly bullied- even by teachers and coaches, to the point he snapped. I doubt even the political environment of the past 2 or 10 years contributed to this. We've been sliding down hill for a long time in regards to how we treat each other, respect, and common civility. But when it comes down to it, the responsibility lays with the kid himself, and maybe to a small margin, with those who bullied him (if true, one could even say he was mentally tortured until he snapped depending on who was asked about his bullying).
