The character in question gets weapons, kills a few people in a spree, police catch him.
They diagnose him as psychotic. He believes to be a supernatural creature. As he failed to achieve his plans he is not violent anymore and gets along with law enforcement, He also takes whatever medications he is given, but when asked with still insist on not being human.
How long would he be in prison and how long would they try to treat him for his psychosis?
Searched for treatment murder psychosis canada prison term in various combinations