You may be wondering how could such a person do destructive and violent actions such as killing, kidnapping, torturing, raping, and some sorts of gruesome behaviors considered as "evil." Meanwhile, you might be surprised of someone doing exemplifying things such as sacrificing for someone, giving, and desire to help other people, which are all regarded as "good." These are the faces of the two social and violent beings, who exist in this world, namely the psychopaths and the extreme altruists, respectively.
Jean Decety, a social neurologist at the University of Chicago, said that humans are the most social species on Earth, and they are also the most violent species on Earth. He further said that they have two faces because these two faces were important to survival.
The origin of how good and evil manifest has been debated by some philosophical and religious sectors for centuries. However, recently, scientists involved themselves in understanding the science behind doing good and evil.
Studies have shown that empathy, which is an emotional trait, played a significant role in both extreme altruists and psychopaths. Empathy is the ability of the brain to be aware of the feelings and emotions of other people. It is how people understand what others are experiencing or going through.