I believe the mental illness that shooters have that makes them such good targets for manipulation is bipolar disorder. This is not fast mood swings but periods of mania that come on over the course of weeks, and the individual is will become progressively more paranoid and potentially more violent. The perfect patsy would be someone who has long been interested in communism/Marxism, has some interest in current politics, has had at least peripheral experience with guns, and has bipolar disorder. Mania is likely purposefully induced to condition the individual into carrying out the shootings. Likely those with bipolar who are on anti-depression drugs specifically are the ones we are seeing.