PLEASE READ THIS: "Baby Animals Which Kills Its Own Siblings for Survival"
Look at the keywords: "For survival".
The killing is still situational in nature. If food was plentiful, and living conditions not the least bit harsh, would any of these baby animals cannibalise their siblings?
BBM: survival seems to fit the role of the military sniper too. And a cop who, if caught in a situation and required to kill, afterwards undergoes an administrative leave of absence accompanied by counseling. It also causes soldiers to have PTSD.
But serial killers enjoy killing other people. There’s no way to know what goes on in the mind of the mentally ill. My personal belief is their brains aren’t wired right thus it starts as nature. I don’t believe they are fixable either.
As an aside, I am a death penalty proponent. Where would people like me fit in? 
When in doubt, don’t.
Probably before the time time of Moses Pat but that’s ok, just makes you old fashioned and there’s nothing wrong with that. I am too 
“I don’t know Chief, he’s very smart or very dumb.“
