"A self-centered, alienated, angry person throws a tantrum, and people die."
We need to learn what it is that turns normal people into violent people. What is it that alienates and angers people to the extent that they throw a deadly tantrum?
With that information we can possibly prevent many of these sorts of violent events and increase the number of persons living relatively happy, fulfilled lives.
In my opinion, focus on the tool or weapon used in violent acts, is misdirected.