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.
When the naval officer arrives on the island in the book The Lord of the Flies, he sees the boys and sees that Jack and his group are dressed in war paint and barely clothes. Ralph is crying and on the ground. He has no idea that the scene is almost Ralph's death at the hands of Jack and his hunters.
The naval officer probably believes that the boys were playing in the forest and around the island some adventure game. He has no way of knowing that Roger had shoved Piggy off the rocks with a boulder or that Simon had been attacked and continuously savagely kicked and beaten. Remember, both Piggy and Simon's body were washed out to sea.
I think the naval officer doesn't seem shocked about the death of the two children is because he is surrounded by death due to the war but also he doesn't want to know the truth of what happened on the island 'he turned away' his lack of awareness is due to his desire to be unaware and that golding is trying to show the biggest source of evil comes from the adults 'the darkness of mans heart'.