What happened to the sniper after he found his dead brother? Did he keep fighting, or did he stop and cope with the loss of his brother?
The final sentence of the story is the sniper discovering that the other sniper was his brother. There is no textual evidence that supports the sniper going back to the war or taking time to cope with the loss of his brother.
If the question is asking "what do you think," then either answer is fine as long as you explain your reasons. Personally, I think the sniper would have sat down to mourn and begin coping with the loss of his brother.
When the story begins, the sniper is painted as a hardened, fanatical killer.
His face was the face of a student, thin and ascetic, but his eyes had the cold gleam of the fanatic. They were deep and thoughtful, the eyes of a man who is used to looking at death.
He's a man who kills, kills efficiently, and kills without remorse. However, that attitude appears to change as the story nears its conclusion. The sniper knows that he has been lucky to survive his most recent firefight, and the months or years of combat are taking a toll on his psyche. The sniper has a sudden outburst of frustration and rage at his situation and the war in general.
Weakened by his wound and the long summer day of fasting and watching on the roof, he revolted from the sight of the shattered mass of his dead enemy. His teeth chattered, he began to gibber to himself, cursing the war, cursing himself, cursing everybody.
I believe those lines show that the sniper is becoming embittered at everything around him. I'm sure discovering that the very thing he is beginning to hate is the cause of him having to kill his brother is the final tipping point. I'm confident in believing that the sniper would have stopped, sat down beside his brother, cried, and thought about the utter stupidity of the civil war that he is fighting in.