Another common thread for many of these shooters is violence or threats of violence toward women. It is sometimes discussed but doesn't get a lot of emphasis. In a society building on misogynistic ideals, it's easy to speculate on why that may be.
https://www.nytimes.com/2019/08/10/us/mass-shootings-misogyn...
https://www.bostonherald.com/2022/05/30/wendy-murphy-texas-s...
Here's where Red Flag laws could do a lot.