I had perhaps the worst nightmare in my entire life due to the fact that it was to me , as realistic as any experience . It starts I am standing in a line in and underground railway like the public transportation you see in the movies in NY or other eastern cities . There are 10 people or so in front of me and several behind and identical lines on both sides , it seems we are waiting to buy our tickets for the Tram or whatever they are called . To my left are perhaps a dozen lines and a set of stairs going up to the street or down to where we are , divided by a handrail in the middle that is maybe 80-100 feet away . I hear a women scream for help to my left and I see her running down the stairs towards me still screaming . As she enters the ticket area she disappears trying to push her way through the lines as I can hear people cursing her for running into them and see the lines ripple as she makes her way . I then see a man running down the stairs with a very long kitchen style knife in his right hand and I turn to my left facing toward them . As the woman progresses she is having to zig zag going for openings between people to stay ahead of the man yet apparently the people in line see he has a knife and are trying to move out of his way so he is closing fast but with people moving back and forth he is popping in and out of my view . As she gets two lines away she is now off to my right by about 3 people and he is heading almost straight at me with his knife about chest high , the two people directly in front of me part and the man is right there as he is coming through the previous line as she is about to come through the last line between her and I . I pull my CCW weapon and raise it and line up my sights on his chest without a warning as I don't want to cause anyone to panic and move into my way , I press the trigger and as I do the woman darts between the two people who parted giving me a shot at him and I shoot her in her chest . I woke up at that point in a cold sweat . The worst part is I don't think it takes much of an imagination to see how this is all to possible in the real world . How would you think it would best be handled to avoid a tragedy of shooting the wrong person , either her or a bystander ?