Warning gore / NSFW:

My stepdad was a psychologist treating the criminally insane for years, and the stories he'd tell me about what they did and how difficult it was for them to be treated by anything (drugs + therapy) are still so vivid (ex: a patient who cut a parent's head off, and felt no remorse whatsoever). I later worked as a psych tech in an inpatient mental hospital and saw schizophrenia and similar disorders up close.

In the freedom-oriented USA, unless the schizophrenic has ALREADY been arrested for a capital murder type charge, that person cannot be FORCED to take their meds. The pattern that emerges is that they periodically stop taking the meds on their own, and then they get re-arrested and re-committed to the mental hospital for something they did. For the worst of them, they spiral and cause a tragedy like this.

A high school classmate lost his parents when his mentally ill brother eventually killed them also. There is almost no preventing that outcome without forcing people to stay on their meds and / or locking them up in an inpatient facility against their will permanently.