bad things happen in war, people act in ways that are deemed bad or wrong in normal society. Its how people deal with horrible things. I never went to war when I was in the army, but was always disgusted by my staff sarge's racism towards iraqis. Then he told me that he didn't really hate them, but he found it very hard to shoot people if he saw them as people, and thought about their families, lives and past. He was dehumanising them, acting in an overtly offensive way to try and make his job and his ability to cope with it easier, in his words, "its easier to shoot a rat than a person.". Its not right, its not my way, but then I'm not a soldier in a war and I don't have to deal with these things.
yeah he shot a dog, its bad and wrong. If he'd shot it at the time it'd be ok, if the dog got blown up by a rocket it'd be ok.
its sad that people act like that, but worse things happen in war.