Very good!
Great story, nice and long. Nice visual style (even if it is over done). Overall very good.
Nit-picky criticisms:
Why put black text in a white box? It was very distracting. Why not just white text, or white text with a white trim like you did for just a small amount of time near the end.
Why am I to assume the people I want to shoot are going be smoking cigarettes in some missions? Sometimes I felt like this game was an anti-smoking campaign. It all boiled down to "wait for the guy to smoke a cig" or "wait for a guy to stop at a window" on almost every mission. If the story wasn't above average for a flash game, this very simplistic gameplay would have held it back.
Cos isn't a word.