I have an anecdotal experience to share. This school shooter I could relate to because I was also in that mental state of him when I was younger 10 years ago or so. Every time I try to rely on what I called friends when I was at lowest point, not only they didn't take it seriously, and I found out they are probably badmouthing me behind my back. Back then I never liked being singled out but they would keep doing that.

What made my mental state better was getting the fuck away from them and completely ignoring them and becoming hermit. Then I stopped spending way too much money and had more time to be productive when I decided to isolate myself. That was when I learned it's not worth it to have socialised life. And if you are in that lowest point of life and depressed, girls in general seem more cruel to you and treat you very coldly. That was way before poltics got crazier and more extreme. I cannot imagine how worse it is now. Some people just don't have much empathy and only seem altruistic if they get something out of it. This is maybe why I become more aggressive if I meet what I assume is left-wing zealot.