[Sekto Springs]

That's really dismissive thinking, bro.
Nothing "just is", especially when it comes to human beings. We aren't "just" anything. We are all complex organisms and every action, motion, and thought is dictated by very specific electrical impulses and chemicals. Faulty wiring can turn you into a fucknut, but if we all thought as black and white as you do, a lot of people who were simply a bit schizo or manic depressive would be lumped in with people who just genuinely loved killing.

Though this scenario is somewhat far-fetched: what if a schizo ran out of insurance, or through some bs technicality, was forced to go without his meds for a period? In this amount of time, voices in his head told him to stab his co-worker because he's an evil alien bent on turning the entire populous intro grapefruit. He kills him.

This is just another example of the gray area that has to be taken into consideration when dealing with these situations. You have to handle them gingerly, regardless of how sure you are the person is just a raving devil.