I have not found what you seek.
A few things I found interesting
https://www.libertynation.com/the-mind-of-a-mass-shooter-or-why-gun-control-wont-work/
https://www.powerlineblog.com/archives/2019/08/mental-illness-and-mass-murder.php
https://www.motherjones.com/politics/2012/12/mass-shootings-mother-jones-full-data/
Interesting.