So FBI considers an incident where 4 people get killed to be a ‘mass shooting’ while Shooting Tracker considers a “mass shooting is when four or more people are shot in an event, or related series of events, likely without a cooling off period.”

The number is in fact real, only its significance is a little different.
Anyway, 355 incidents in which 4 or more people were intentionally wounded by somebody else is a lot.
And I really don’t care about how they got wounded. Regardless of being shot, stabbed or whatever, it was a fellow human (?) that did it.
What was it that drove these individuals to do such extreme acts?