The issue is that the drugs don’t work the same way for everyone, and can stop working for a person.
The shooter was 20. He may have stopped taking his meds, cut the dosage, or they stopped working.
Meds won’t cure a condition, they treat the symptom. There are people who belong in institutions, non on meds.
I agree with all you said, every bit of it, and my view comes from personal experience with extended family who were downright dangerous and determined when off medication.
That said, I think the original article was a lame attempt to blame the drugs for the actions of the deranged.