I like the concept of the script. Tying all the loose ends together believably is difficult. It seemed like you were figuring it out as you went along, and when you needed to insert a bad guy you would do so. I liked the whole plot, and how you built the story around a secret deal with the chinses government for weapons.
I had a big problem with Derek throughout the script. His personality changes from one extreme to another. First, he starts off confused and scared, then he becomes rambo, killing off gang members and assasins. This would be a huge extreme to show on camera. If you were going to show him taking revenge, do it on a smaller scale. One guy. One gun. By keeping the reality level down to earth it makes the story more believable.
The other characters who switched back and forth were Det. Riley and Elizabeth. Either one liked Derek or the other hated him. One minute Riley is begging for a chance to prove Derek's innocent and then he's saying how he wants the bastard locked away and how he wants to kill him. You have to stick with one central path for your characters.
Again, this is a very difficult script to write. Professionals have a tough time, creating a unique plot, as well as interesting characters and still giving the audience a surprise at the end. You got two out of three. Not bad. Figure out exactly what it is you want the story to be and build characters around that. Also, one last thing, you can cut down your descriptions a lot. We don't need to know how sticky the floors are. Good job man.