Cat's a little bit insane though xD he just acts a bit more like a wild animal than a actual human. 

Since he has 0 understanding of humanity or morals.

Crazy survivalist. Killing being a simple (and fun) solution.

But at least he won't stalk you! (Watch but not stalk) :D

But yeah, Psychopath is it's own definition of insanity. (Cold-hearted, yet highly intelligent, buts Iacks empathy for others.)

While Insanity has a whole different aspects of it <.<

Like 

Psychopath: The serial killers who lack concern, empathy, guilt for others. In touch with reality, and get a thrill off of killing people.

Psychotic: The insane. Out of touch with reality. Have delusions and hallucinations. Though not really wanting to kill people. (Unless the hallucinations tell them too).

Fun stuff you learn :D