I said it before and I'll say it again: Humans tend to opt for the lower, baser, primitive instincts of our nature. Humans also learn things by observation and imitation. When faced with an enemy whose ethos preaches, supports and glorifies no-holds-barred hatred and violence some humans will respond in kind. 

It is a law of nature. 

To prevent this, we have created civilization. But "Civilization is not self-supporting. It is artificial. If you are not prepared to concern yourself with the upholding of civilization -- you are done." (Ortega y Gasset).

This is what happened with these murderers. They gave in to the most primitive of rage. What I would like to know is what is their relationship with civilization and how come they grew so wild that they could even come together, think together, plot and carry out such a horror.

More important I want to know who is truly responsible for turning these persons into murdering monsters. Who is the inciter? Who told them this can be done and that it is right?