>>it depends on what's meant by mass shooting - and apparently some will count even if there aren't fatalities.
According to the FBI it's a mass murder if 4 or more are killed. Mas shooting means 4 or more shot.
Did you check out what the Alabama Criminal Justice professor had to say about the underlying cause of all this?
"... They ne'er cared for us
yet: suffer us to famish, and their store-houses
crammed with grain; make edicts for usury, to
support usurers; repeal daily any wholesome act
established against the rich, and provide more
piercing statutes daily, to chain up and restrain
the poor. If the wars eat us not up, they will; and
there's all the love they bear us."
-- Shakespeare: Coriolanus, Act 1, scene 1