State of society is the root cause
Hollywood produces and promotes violent movies that glorify killing without any consequences. Video game producers sell video games that promote violence and challenge the players to kill as many human beings as possible. We are losing discernment between right and wrong. School children who appear to be disruptive are put on prescription drugs such as Ritalin. Is it any wonders kids develop mental health issues? In school children are taught that they evolved from an animal. Is it any wonder that they act like an animal?
Until we recognize the ethically degraded state of our society, we cannot address the causes of, and put a stop to, these mass murders.
Focus on the causes, not the symptoms.