if you look closely at michael's face, his eyes and expression reveal to me that he saw something/someone outside the window a spllit second before the shots.... Go back, check it out!
Of course he did...it was his cue.
Remember it is a movie.
Do you really think that FFC would let such a blatant "cue" into the movie? Am I to believe that Al Pacino 'though still a young actor' was not showing his brilliance as an actor to portray such a dramatic "look" as just a "cue"? I disagree, there was clearly more going on there than just 'sloppy' editing......