Revealing mistake: When Adams is inside the trench and dirt begins to pour, he is replaced by an obvious stuntman with a totally different hairstyle.
Revealing mistake: During the car chase (an obvious rear projection), Lew keeps turning the steering wheel around despite the car driving straight. (00:09:39)
Revealing mistake: When Denise picks up Corry, he has a silver patch underneath his shirt. Seemingly some sort of protection.
Revealing mistake: When the highway collapses, the miniature prop is missing the delineators and lamp posts.
Revealing mistake: During the jolt by the dam, the worker's table shakes, but not the rest of the stuff surrounding them, revealing that someone was moving the table underneath. (00:05:58)
Revealing mistake: Near the beginning, after a couple of small earthquakes, Fred comes flying out of the dam elevator shaft with a whole heap of water, dead from drowning. But you can see him lift his head out of the water seconds before his friend turns him over and finds him definitely dead.
Chosen answer: Before he put the uniform on, he was a complete nobody, having the respect of no-one. Now that he's in uniform, he demands that people should respect him, and coupled with the powers of Martial Law (where looters can be shot on sight), takes the lack of respect too far and shoots them.
GalahadFairlight