The worst thing a potential victim can do in an active shooter situation is to freeze in position in a state of confusion or shock. Unfortunately, this is also the most likely response to sudden violence (even if just temporarily), so it’s vital to prepare people for this possibility, and get them thinking in advance about ways to recognize and fix this problem if it occurs. Forewarned is forearmed.
It turned out that our “posse formations” simply took to long to organize. By the time cops rounded up four to six officers to make entry, the attack was finished. Our group entries weren’t saving lives, they were causing more deaths
Putting on the show, wearing the coat of authority over topics you have no personal experience with makes you a poser. Look for instructors who site their sources, and own it when they have no first hand experience. That doesn't make them bad - it means they're aware there are topics they haven't faced.