Seattle

But in schools, being gun free zones, "civilians" are legally not allowed to be "armed."

There have been "mass shootings" or "active shooter incidents" stopped by armed civilians in places where guns are allowed like churches, parks, malls, etc, even when carrying there is a legal grey area (signs posted but the state doesn't prosecute carrying there).

But of course since guns aren't legally allowed in "schools" (like, federally, at all) you of course won't find any "armed civilians" at all, as the only ones willing to bring in a gun are the shooter themselves (because duh) or the cops (who are allowed by law to do so), not civilians (who are legally prohibited from doing so), for obvious reasons.