The story is told from the third person limited point of view, meaning that a narrator who is not a character in the story tells the reader the tale (this is the "third person" part). The "limited" aspect of the point of view is applicable because the narrator focuses primarily on the sniper's actions and motivation. We don't know much at all about the enemy or what he is doing/thinking. Liam O'Flaherty most likely chooses this point of view because it helps the reader feel how isolated the sniper is and how painstakingly meticulous his every move must be. Similarly, because of the limited knowledge that the narrator provides about anyone or anything other than the sniper, the reader--just like the sniper--does not know what the enemy is up to or if the main character will survive.