"Acts of violence such as active shooters aren’t random,” says A. Benjamin Mannes. “From events such as Adam Lanza and Newtown, Nikolas Cruz and Marjory Stoneman Douglas High School, Jin Yu Park at Virginia Tech, and even Jared Loughner, who shot Congresswoman Gabby Giffords, all were planned.”

https://www.securitymagazine.com/articles/89265-in-a-days-work-the-fight-to-end-workplace-violence