The setting of Liam O'Flaherty's "The Sniper" throws readers in media res (Latin--in the middle of things). It is dark, and machine guns and rifles are lighting up the night. It is the middle of a civil war battle. As frightening as a war is, the fact that this battle is taking place during the night compounds the anxiety. Paragraph two introduces the readers to the protagonist, a Republican sniper. Perched atop a roof, the sniper's "deep and thoughtful" eyes reflect the death they so often see. As the story continues, the sniper takes the lives of his opponents. Without fear, he inhales his cigarette and shoots at his foes. In the end, the sniper gets his man (another sniper).
The setting, the middle of a gun battle, forces action and conflict. This scene is natural for conflict: two opposing sides fighting for their own ideologies. Given the civil war raging around them, it would only make sense to focus upon a soldier and his "prey."