Yes it does appear that all or most of these shooters are angry white boys, and I don't know the answer. Metal health must be an issue, to be that fucked up that killing indiscriminately could possibly make you feel better, or relieve anger.
I still don't want to give up my guns, but I have no perpetually angry white boys in my family.
I did have a nephew that was headed down that path, but now appears to be out of it, and I believe girls did it. Once he figured out what girls are for all his anger seamed to fade. Now In college with a steady girlfriend and confident, doesn't act or feel like the misfit he portrayed himself to be he was in early in high school.