There is no “potentially” when the LEOs are standing around posing in their unused tactical gear. At least they won’t get reprimanded by HR.
Nothing is, or was guaranteed that day, even if a number of cops had stormed the school. You might like to think everything would have gone well, but potentially, it could have also gone very bad. We’ll never know, but continuing to assume specific scenarios would have occurred, doesn’t do anyone a bit of good.