A democrat prosecutor may analyze shot by shot and question a few of the shots, but I doubt that he'll get convicted (just bankrupted with legal fees). The world is better off without the two terrorists he removed, but he would be much better off without having been in that situation.
Note: I've been in a position where I could legally have fired (multiple home invaders, police VERY slowly on their way . . . 20 minutes later), and the world would have been a better place without the criminals I was facing. I chose not to pull the trigger because there is a difference between being legally permitted to shoot and really having to shoot. I'm still not sure I made the right call, and I wonder what choice this guy would make if he could have a do-over.