Lots we do not know.
But, the lessons learned from Columbine and Parkland were supposed to result in a very fast response.
The troops are not supposed to wait on orders or form more than a quick battle plan.
Well that was my point up thread. They didn’t initially sit back and wait. There is a dead cop. No? There was a reasonably fast response and one cop paid the big price when he went in. I would suspect it was a uniform patrol cop who had light protection. He he could have been the one who shot and injured the suspect. Regardless, he went in and died doing his job. I’m not going to fault someone like that or imply they didn’t do their job. Not in this case.