For the individual armed citizen, an Active Shooter situation is the prototypical Black Swan event: Low probability but very high impact if it happens when and where you are. And in the wake of recent reported shootings it can and has been a very worrisome situation for any such concerned defender. What can you do to prepare yourself to deal with such a thing? What are your options when face with such a horrific attack? What do you need to know and what do you need to do? This is an attempt to provide not specific answers to detailed situations, but a series of guidelines and suggestions that can be considered and used by anyone without specialized knowledge or training to prepare their own answers and their own approach to this test. It attempts to gather, organize, and outline a framework around which specifics can be built according to the ability, knowledge, and experience of the individual builder. It is a compilation of ideas from many gathered from many places and many people. It not the answer itself, but an attempt to give you, the armed citizen who may one day be the real first responder to this kind of attack, some help and some basis for forming your own answers to this very serious question: What can I do if...? My hope as the author/organizer of this material is that no one reading it will ever have to find out how useful it is. But just in case that hope is not fulfilled, I hope that something in this will help you keep yourself and your loved ones alive and whole. This revision includes additional information and examples based on what has been learned and is known about the most recent attacks. Sections discussing attacks with vehicles, bladed weapons, and options for when you don't have a gun of your own among others have been added. I am one of the few and perhaps the only author that continues to revise and update the material in their books in this way and I will continue to do so. The enemy is learning and adapting. So should we.