It's a Start
You look like a new flash artist, so let me give you props on this. It's well done, but there are a few things you need to fix up. The shotgun sounds terrible...
While it's not the biggest thing in the world, you might want to see if you can get a better sound for it. Secondly, add a reload button. Make R the button to reload your shotgun so it's easier and not leaving you too vulnerable. Thirdly, add a reloading animation so you can see the shells go in the shotgun. Next, try and get more then a pop-up shooter. See if you can advance further in a level. It sounds like a lot of work, but you don't want a game that is so repetitive it feels like a pop-up book. Finally, definetly see if you can try to maybe add new weaponry? Shotgun isn't that great, round after round. Making just a spare little pistol with 12 rounds, and the shotgun with 6. Just for a little variety?
You're well on your way to being a good animator. Keep up the good work.