Tips on what to do during a mass shooting, shift mentality to not 'if' but 'when'...

Tips on what to do during a mass shooting, shift mentality to not 'if' but 'when'...: Watching the news of mass shootings, you almost always hear someone say, I can't believe it happened here.  Now, experts are saying it's not a matter of if it 'might' happen, but 'when'.  And, when it does, are you prepared?