As news of another senseless violent incident reaches us we find that reflection on the history of human violence is helpful. Violence had a dramatic effect on the Creator of heaven and earth and a fresh start was his judgment. In the 21st century widespread violence and murder are complicated by the suicide of the perpetrators. There is a graphic illustration of this murder-suicide phenomenon. Judas.
And after the sop Satan entered into him. Then said Jesus unto him, That thou doest, do quickly.John 13:27
Judas proceeded to finish his deal with certain of the leaders.
Judas then, having received a band of men and officers from the chief priests and Pharisees, cometh thither with lanterns and torches and weapons.John 18:3
And he cast down the pieces of silver in the temple, and departed, and went and hanged himself.Matthew 27:5
I am suggesting that suspect #1 in murder-suicides demonic influence, if not demon possession.