@warbow150 (Since the @#$% reply/ quote widget won't work
as is now usual!)
If a gunman is barricaded in a room with multiple persons who are not his willing co- conspirators, those people are, by default, his hostages.
My interpretation is that's what happened here. The suspect's intent was to be an "active shooter" and go throughout the school, killing as many people as he could. However, due to the intervention of the SRO, his plan, such as it was, failed and he ended up as a barricaded hostage taker with significantly less ammo than he originally brought.
The scenario started off as an "active shooter," but within minutes, possibly within seconds, and before any additional law enforcement arrived to assist the lone SRO, it became a "barricade/ hostage situation."
I've been retired for almost three years now and it's been at least 5 years since the last time I did active shooter, but the response shifts gears from "seek and destroy" to " negotiate/ bring in the entry team" once the shooter is confined to a specific, enclosed area and no longer actively shooting people. At least that's how we did it.