[pjc50]

> incidents involving 4 or more school deaths

That number seems suspicious; you'd get a very different answer if your criterion was "any gunshot wound at a school", for example. But that definition might be a better match for what people think of as a school shooting.

(e.g. Northern Ireland had a very large number of terrorist attacks where a warning was given allowing evacuation - would they not count as terrorist incidents even if nobody was killed? I suspect not)

[toast0]

Any gunshot would at a school probably includes a very different pattern of behavior. If someone wants to murder (or maim) a specific person, or small group of people, they may carry that out with a gun, because it's expedient, but might switch to a knife if guns aren't available. If someone wants to murder (or maim) a large number of people, guns or explosives are really the only practical means; mass knifings have happened, but are even more rare than mass shootings.