FUCK THE POLICE
911 EVERY DAY
In Arizona they have an option for "Guilty by Reason of Insanity", where he'll go to a shrink, but when he's fixed he goes to prison to serve his sentence. In this case, with multiple murder victims, it would likely be several consecutive life sentences.
Actually it's "guilty but insane" ("Guilty by reason of insanity" would be nonsensical), which I think is a dumb idea. If you ignorantly blame actions that happened due to the presence of a mental illness on the individual rather than the mental illness, you may as well just render a "guilty" verdict, and send them to special facilities designed to deal specifically with the insane. There's not really any reason for a separate verdict. In the case of "not guilty by reason of insanity", there is a reason for the separate verdict (mandatory detention in a mental hospital).
There are special legal protections for some insane from the death penalty, but I'm not sure exactly what test is used to apply it. It may just apply to people who aren't capable of understanding what's going on. I'm reasonably sure it's not dependent on whatever prescientific standards the government in question chooses to apply to pretend that they have an insanity defense.