BBM Great post. Believe it was in the '80's a psychiatrist named F Scott Peck wrote a book titiled "People of the Lie." After practicing in mental institutions for many years, and dealing with broken families and individuals, he came to some conclusions and presented his thesis in the form of this book. He came to the conclusion that some individual's, while being neither mentally ill (by the DSM's, Diagnostic Statistical Manual of Mental Disorders) standards nor necessarily criminal, defied categorization. Thus he proposed the DSM add a new category and label it 'evil.' I found the case studies in the book fascinating and his idea brilliant. It was criticized by the scientific community as bordering on religion, which I did not necessarily agree with. Regarding the nature vs nurture debate, Dr Peck proposed that we are the sum total of our life choices. Beginning in young childhood, we are presented with choices every moment of the day: how we use our time, how we respond in a given situation, how we relate to others, etc etc etc. The effects of our choices over time determine our character, i.e., who we are. Good/right/proper/correct choices point us in one direction, while bad/improper/inappropriate choices point us in another. It is difficult to explain but if anyone is interested, I do highly recommend reading his book. It was a real eye opener for me. That said, I do believe we are the product of both: nature and nurture.
ETA Hope this isn't too far off topic (it was discussed in many posts.) To go back on topic, that meltdown provided much grist for the mill. Lots of analysis to consider further.