Good Start...
This works really well as a little prequel to a more rounded and fuller game. As it stands at the moment its a nice distraction for a little while. The lack of colour is what lets you down the most, but after a little while of playing it the lack of colour added a certain kind of strange charm. ^^ The shooting action was smooth and i had no errors, it was responsive and the aim was great, so the engine works perfectly. With a little addition of colour and perhaps something to replace the slightly grating chainsaw noise you have the premise for an enjoyable, classic 1st Person Shooter Flash Game.
I look forward to seeing your updated version. =)