which still begs the question , as it is not other venues that get targeted , what is it about the US school system or social environment therein that garners such extreme violent behavior from some ? 

Is there a common denominator ? Are there common factors ? ie Do those schools promote an accepted culture of distain and prim loathing amongst peer groups ? I ponder , there has been some hints from some of the surviving shooters , as there was from our own M***** B. that allude to a rationale ( a rationale unjustified but still a rationale ) 

But nobody seems to be asking this question.