Earlier quoted context omitted.
In situations like this mood is extremely relevant. Its what separates the disciplined professional from people who whine and second guess things. What many people don't understand is that a wrong decision is better than no decision at all. The world isn't going to wait for you to call an assembly and have a cordial discussion about how to delicately make a possibly-suicidal suspect feel happy. It sure as hell isn't…
You didn't explain how mood should inform operational doctrine. My claim is that it should not.
Operational doctrine here suggests that, with active shooter, you prioritize removing the shooter once negotiations have failed. The "probably would have" the poster is referencing is a what-if they didn't have time for.