At the end of Lord of the Flies, I've always been a bit puzzled by the naval officer's reaction to the bloodied Ralph myself. I expected him to be a bit more shocked or sympathetic to Ralph's and the other boys' condition. However, as the previous post pointed out, the officer has probably seen his share of fighting and death during his military service, so he may have realized that this was a part of life everywhere. He may also have considered the plight of the boys and their long and difficult stay among the primitive surroundings when he turned away at the end to let them compose themselves.
The answer to this is not exactly given to us in the book. The officer does not really say anything much. But I think we can have some ideas.
My assumption is that the officer is not more shocked because the country is at war and has been for quite some time. It seems likely that he would be way more inured to (used to) the horrors of war and how bad people can be to one another. So I think he's just gotten used to people being evil and so he's not shocked.