I agree. Mentally ill kids who end up committing these horrible crimes are almost always going to have a history of mental illness and incidents. Histories of mental illness will almost always result in attempted treatment. Attempted treatment is extremely likely to involve psychiatric mediations. These do have positive effects on many cases, and are more effective than alternatives; unfortunately, no sure thing, permanent remedies exist. But mental illness is a dynamic phenomenon. Meds can be discontinued; the physiology of the patient can change, rendering the prescription ineffective or harmful over time.
The relative success of psychiatric meds creates a societal problem by providing an excuse to cheap out on keeping a close watch on the patients. They’ve had “treatment”, and appear to be ok, so it stops being a public concern. Society pays attention AFTER something extreme has happened. Because all it takes for a disaster is a tiny fraction of cases to become hyper-violent, our “system” for dealing with this is guaranteed to fail. Family members, if any are even involved, have many motives not to be effective guardians of a young adult’s mental health issues. They don’t want to make life worse for their kids, and can be expected to get used to, or rationalize away (”it’s just his art...”), problem behavior an outsider would see as major warning signs. At worst, they can want to pretend the problem away for careerist reasons, like wanting to be mayor, or simple denial that their kid has a problem at all. Then there is the problem of kids aging out of their parents’ control.