Actually, I’ve had some training in this. The “best option” depends entirely on the situation, where you are located, what you have at your disposal, etc. Often times, running away is the best option. Sometimes, fighting back with whatever you’ve got is the best option. “Taking cover” is not usually the best option, but it that’s what you’ve got to work with, there you go. Furthermore, there’s a thing called trauma response, which means that when a person is in a mortally dangerous situation, the defense part of the brain takes over and a person doesn’t really have a whole lot of control of what they end up doing. They may be completely unarmed and the adrenaline kicks in and they tackle the guy from behind. They may be armed to the teeth and still completely freeze and pee their pants. And you seem to assume that the gunman is going to make a big announcement before he starts shooting. He could have you in the back of the head before you’ve even turned around. So, yeah, I do have a little bit of training in how violent encounters work in the real work. They aren’t something that you can “plan”. So you might as well just go to Mass and pray for the best. And confession is also a good idea.