IMO
this person is severely mentally ill,
and his condition has manifested itself since childhood.
He seems unable to lead a normal, independent life,
(school, job, starting his own family)
and had always been dependent on parents.
What exactly would be the motive
if he was treated as sane?
I suspect delusions, hallucinations, paranoid psychosis
(especially as his meds were being changed).
IMO
his place is in a psychiatric facility, possibly for life.
That is my AMATEUR Opinion.
(As I'm not a MH specialist)
But really,
all I read about this tragedy confirms my view on this case more & more.
JMO