Before I take a shot at this (no pun intended), I want to help you with your sentences. "There are 10 birds on a tree branch, but a hunter sees them and shoots them with a gun. Now, how many birds have been killed?" Now, my guess is that there could be any number of them dead or none of them dead. You said the hunter shot them, but you didn't say the hunter killed them. Maybe they are just injured and really, really unhappy with the hunter. :P

i think they all flew, they scared of the sound. may be just one of them shot...