More stories like that seem to surface each day. My guess is that violence perpetrated on a large scale (ie: war) combined with violence in the media has normalized it to an extent. So that when anger and discontent arise in the lives of emotionally unstable people, they're far more likely to see violence as a viable solution to their problems.
You're thinking of the Socialist/Communist approach to dealing with "problem" people. (How many lives did Hitler, Stalin and Mao snuff out in their quests for Utopia ?)