This is very interesting!
I would think there is something in between the experience of childhood trauma and the onset of the crisis in the weeks/months leading up to the shooting (between the first and second items on the list above).
Plenty of people experience trauma in childhood and who manage to go on to live healthy lives. Not every child who experiences trauma later shoots people. So I'm thinking there must be another common denominator that indicates the child never healed from the trauma. THAT missing link is worth finding, imo.
In fact, some people who experience trauma as children or later in life credit that trauma for giving them strength, determination, sense of connection to people who helped them, purpose, compassion.
Trauma doesn't need to lead to life-long anger and eventually violence - but in these mass-shooting cases it seems to. What's the difference between who recovers from trauma and who doesn't?
jmo
In my humble opinion these shooters are not "alt-right" or "nationalists" or "nazis".
I think they just have some (huge) mental issues and they use nationalism, nationalsocialism or any other ideology just to hide their psychosis.
There is no insanity defense any more. Millions of people with psychological issues mange not to kill people. The individual that killed, who took actions to kill others is the one responsible.