"Why are bad guys bad"

I had mentioned a powerful RadioLab podcast in class last week about a prolific serial killer, the Green River Killer, who was never really able to understand why he killed. I made this reference to connect with Eva's inability to understand why she killed Davis and that maybe the deep, underlying reasoning for the killing of another human being may never be understood.

7:30 is when the story begins on the RadioLab podcast titled "Why are bad guys bad?": http://www.radiolab.org/story/180166-why-be-bad/. It's really a fascinating story that is worth your 10 minutes of time! 

After an intensive interrogation with Gary Ridgway, the Seattle-based serial killer, special detectives tried to get Gary to divuldge the details and secrets to the 49 murders of female prostitutes, including the one question that everyone really wanted to know: why?

Gary's most satisfying confession still does not present us with a concrete answer, "I just needed to kill because of that." Neither Eva nor the people around her seem to understand why she killed Davis, but outsiders seem to believe that there must be a true reason hidden beneath her silence.

In Gary's case, after talking to psychiatrists, forensic psycologists, and detectives, a clear patter in conversation would begin and point to the musing that we would never figure out the underlying reason why some humans kill other humans. 

I needed to kill.

Why?

Because of the rage.

Why the rage?

Because women have stepped on me my entire life.

Well, why couldn't you have delt with it in normal manner?

We will never understand what makes these "bad' people different from the rest of the world, other than that they have successfully killed another human. We are unable to discover the difference between our brains to truly understand what it is exactly that makes those humans kill other humans. But would this belief relieve Eva of the pressures to explain and understand her own brutal actions?