"defines a mass shooting as an incident with at least four injuries or deaths, not including the shooter."
Which isn't really a good definition. "Mass shooting" invokes an image of someone showing up at a school, church, grocery store, some other public place, with the sole intent of killing as many people as possible.
That's not what's being tracked here.
The classic example tracked by the Gun Violence Archive is this story from my own town:
Two brothers had an illegal marijuana grow. 3 guys from Texas roll up at their house to buy the weed.
It's not clear what went wrong, but words were had, guns were drawn, both brothers were shot and killed, 2/3 Texans were shot and killed. 3rd was arrested later.
Gun Violence Archive - ZOMG! Mass shooting!
No, that's pretty average drug crime right there. No innocent victims, everyone involved was engaging in illegal activity BEFORE anyone got shot.
Going through the stories on the Gun Violence Archive, you'll see a lot of arguments turned into bar fights turned into shootings and so on. Parties that got out of hand, stuff like that. Scenarios that are completely different from some idiot intending to shoot up a school, or target a minority demographic.
Lumping together all of that under the "Mass Shooting" umbrella sure gets people scared though.