Pretty addictive! I see potential.
A fairly original Flash game overall, so I found myself playing it an awful lot. Most of the time when I die a whole bunch in Flash games, I just move along, but this one had hooked me to keep getting better. Each level has a learning curve, and I like that.
Of course, there are some areas to improve. The level design was one place. Which enemies were able to see you at each time could have been more clear cut and obvious. Also would have been nice to see enemies walk around instead of just standing in place and looking left and right. Some better AI would make the game feel much more realistic, too. They were always just getting stuck on walls. Also a number of clipping sorta errors. Bullets, dropped guns, blood splatters going through walls and the like.
Now don't take that big list as meaning that I think the game was damagingly flawed. I wouldn't waste my time writing a big review if I didn't think the author had the potential to take something from it and better his game-making skills. I just think that this is a great idea that could be really fun with some improvements to mechanics and graphics. A forced sequential series of missions following the same story would be neat too. Hope you make a sequel.