True and the vast majority of mentally ill people would never even contemplate a mass shooting, but the people who commit mass shooting (or spree killings or serial killings) seem to have a much higher incidence of mental illness than the general population. At least by some research from 2017, the rate of serious mental illness in mass shooter was around 60%. Which is significantly higher than in the general population. https://www.latimes.com/opinion/op-ed/la-oe-duwe-rocque-mass-shootings-mental-illness-20180223-story.html