If his actions become analyzed, his stance is in fact an odd one. His justification for killing the soldiers was that he was saving people by killing those are killing killers. His job as a psychologist was to listen to others as they talked about killing his religious brothers, people he identified with. He could only take so much of hearing their horror stories, of all of their gruesome deaths.
In his eyes, he was doing justice for his people, by killing those who had killed his people.
I don't believe this justifies his actions, because what he did was completely wrong. It's just that we need to identify the root cause of his actions. He is/was sick in the mind, and is a danger to society. I agree with his punishment.