It is gradually becoming clear that there is a chemistry to these mass shootings.
In no particular order, the ingredients seem to include:
1. Mental illness
2. The sense of isolation and loneliness resulting from difference.
3. The conversion of isolation into resentment at the perceived cause (a cause that is usually skewed by mental defects)
4. Crystallisation of resentment into jealousy of a group that is thought to represent the perceived cause, typically including family members.
5. An imaginative spark (exposure to violent movies and/or video games) which gives the resentment focus and removes the normal sense of restraint.
6. The intense desire to right the wrong and to justify one's self.
7. Even the sense of glamour and empowerment these folks often seem to gather from acts of extreme violence.
8. Access to weapons
It's easy to see how a person without the usual doubts and checks and balances can go down this path.
Also leaves a lot of forks along the way that may be used by mental health professionals to turn high risk people in constructive directions.
Especially, provide new models of social inclusion for isolated people.