I believe the Prozac issue here was that he had stopped taking it a few days before the shooting. Arguably this wouldn’t have happened had he stayed on his meds?
Sounds like a guardian should’ve been making him take his meds in front of him/her every day.
Barring that, institutionalize him to keep him on his little pill cup.
If mind controlling drugs are required to keep a walking time bomb from exploding, then I would believe it critical that the patients doses be physically monorored rather than being put on the honor system.
Just because someone is getting treatment or therapy does not automatically make them safe on the streets. The Prescribing doctor has a responsibility in this as well.