There is a perfect storm of conditions that lead to these shootings, I think.
Isolation. Social Alienation.The only place to vent or find comfort is in radical communities.
Feeling powerless day to day. Anger towards those around you. Distrust of the systems you operate in or in the social support systems that you should be able to rely on.
Feeling things will never get better.Lack of emotional awareness or proper emotional outlets.