I always thought instinctively people would immediately look for cover. Second priority is to hide (a hidden target is NOT a target, and a gunman in these scenarios isn't going to waste time playing hide and seek)...but running away is a good way to get a bullet in the back. Guess I just think different. That idea of flattening against the wall is pretty neat. Not sure how effective it is (on a non-curved wall), but going from cover to cover while heading out, is a sound strategy.
I'd like to think that I wouldn't use another as a human shield (and then play dead myself), but in the heat of the moment, and if trapped with no other strategy available, can't say I wouldn't. (especially if I was boxed in).... My first choice though, would be to find cover.