I'm certainly not defending the man, but please don't play into the old stereotypes about the mentally ill. Mental illness is an actual illness, that is usually treatable. And, only a small percentage of the mentally ill are violent (a much smaller percentage than the general population). Poor journalism, as well as the ever-popular horror movies about "escaped mental patients" do not help this stigma, which modern nations should not continue to ignorantly support.

Some murderers are just evil, and are not mentally ill (but they may try to hide behind a mental illness defense). They are supposed to go to prison, instead of psychiatric hospitals for the criminally insane. You may deal with mentally people every day and not even realize it, because they have been successfully treated.