Did you see footage of the guy's trial? He was very aware of what he did and still believed he was in the right. He planned out his action well in advance. Those aren't the actions of an insane person, just someone who places no value on the life of others.
You have to be mentally ill and unaware that what you did was wrong. That's why no psychopath has ever gotten off on Insanity. People with APD are aware that what they are doing is wrong they just don't really care.
Exactly, he knew what he was doing. That is the legal definition of sanity.