Snowflakes in hell has some analysis of the 20/20 piece “If I only had a gun”

A couple of quick thoughts:
The police don’t normally get as much training as the show says they do. Typically, basic law enforcement training is 720 class hours. This includes all of the law, driving, procedures, and firearms training. In my state the firearms portion of this is about 40 hours. I don’t know that they teach some zen-like control of heart rate.

Active Shooters don’t tend to be trained firearms instructors. While some active shooters have gone to the range and practiced with their guns, none of the recent ones that I know of were trained shooters.

Armed students wouldn’t always sit in the same seat in the classroom. From the video it appears that the defensive shooter was always seated in the same spot in the classroom.

There is no guarantee that there is only one defensive shooter. In the general population of my state roughly one person in twenty has a concealed weapons permit. I can’t speak to what is a normal class size, but I don’t recall many courses where we only had roughly eighteen or twenty students.

Some people in the classroom might have more training than law enforcement. There are a lot of students and teachers in colleges right now that have recent combat experience. For many of these people the active shooter scenario wouldn’t even be the second gunfight they were ever in.