Ms. Armstrong says Whittington should have announced himself upon approaching Cheney. That is right. At the same time, Cheney, as a shooter, has an obligation to be aware at all times of the whereabouts of the dogs (who don't announce themselves) his fellow hunters, the guides, dog handlers, etc. I've been on hunting parties of ten men, and it's the obligation of the shooters to know where each of them is, and to be sure they are safe. Cheney knew Whittington was chasing a bird. If he could not see Whittington, if he was not 100 percent sure of his whereabouts, he should not have taken a shot. No bird is worth it.
That's just common sense. Of course there's more to this incident and if you want to know more about it, go on over to Smirking Chimp where there are several articles explaining why the official story sounds really fishy.