Schools shootings were perpetrated by the lonely, awkward kids that didn't fit in. Until the troons took over.

Before the schools, you had people "going postal" at work, so known because multiple postal workers shot up their work place. There was also a slew caffee/restaurant shootings like the Texas Lubys and the San Ysidro McDonalds shootings.

It has always been a social contagion, where groups lash out at those they perceive to be more successful than them, happier than them or the cause of their failure and misfortune.