We aren't actually told very much at all about the other sniper that the sniper who is the focus of this excellent short story has to face and kill. We know that he is positioned on a rooftop opposite to the sniper who is the main protagonist of the story, and that when the sniper reveals himself by shooting at the informant and the soldiers, the other sniper then shoots him. The first time we actually see him comes when the sniper has managed to trick his opponent into believing he is dead, and thus his enemy stands on the rooftop opposite, "with his head clearly silhouetted against the western sky." He is then of course shot and tumbles off the roof, and the sniper goes over to see the face of the man that he has killed, only to make a crushing discovery:
Then the sniper turned over the dead body and looked into his brother's face.
The identity of this other sniper then was the central character's brother, which of course highlights the theme of the story, which is the way that civil war can divide communities and even families themselves, with tragic results.