As my wife and I continue in our slow-motion move, today she got to a pile of paperwork from when she taught in brick and mortar school. It was shocking how much of it was about school shootings and what to do. When to run, when to fight, what to do with your students, how best to break out windows, what to do if someone's been shot, how to take on an active shooter with only your bare hands, etc. Reams of paper dedicated to it.
Honestly, if any teacher escapes uninjured, physically, it's kind of a miracle if they don't end up with PTSD. And this was true before a pandemic.