Answer:
I'm not sure if this is what you're looking for, or if your question relates to a specific story, book, or passage, but I think that it's because there's a certain cowardice and apathy in being a sniper. You aren't ever near enough to see the person you're killing, so you never have to think about the person whose life you're taking. The irony is that one who never sees their victim, who never has to see the blood from the wound, or the tears from their vitcim's loved ones, should not have to wrestle with feelings of remorse as other soldiers do. But this sniper feels remorse as they take this person's life, even from the other side of the street, even from a place where they can't see them.
I'm sorry if this doesn't help, obviously this is just my take on it, there are definitely going to be other opinions, don't feel pressured to go with my thoughts. I suggest you try to expand your own thoughts, and formulate them into a cohesive idea, because having your own thought processes on things is pretty cool in itself.
