schizophrenia + [LSD]/programming =how to create a mass shooter

Already cannot distinguish reality from false inputs.

LSD/programming to create a pseudo-reality of your choosing. Patient does not have tool set to distinguish this as different.

Program them to behave however you want.

Put in place a social support network that captures pre-psychotic or first-break psychotic episodes. Direct their care to programmer of your choosing once suitability is confirmed.