If the question is asking if the sniper had a moral dilemma about shooting the enemy sniper, I'm sorry to say there isn't a moral dilemma. The sniper has just killed the old woman and the soldier in the vehicle. The protagonist has been wounded in the process by the enemy sniper. He knows that he's in a tight spot. He can't stay on the roof and hide until morning because the enemy knows his location. The sniper knows he has to kill his enemy or will be killed himself. 

Morning must not find him wounded on the roof. The enemy on the opposite roof covered his escape. He must kill that enemy and he could not use his rifle.

The dilemma he faces is a tactical dilemma. He has been wounded and can no longer lift his rifle. He has to figure out how to kill his enemy using only his revolver.

The sniper comes up with a ruse to expose the enemy sniper. It works, and the protagonist then shoots and kills his enemy. In fact, the protagonist is excited and eager about the kill right before he pulls the trigger.  

The Republican sniper smiled and lifted his revolver above the edge of the parapet. . . His hand trembled with eagerness.

Then when the smoke cleared, he peered across and uttered a cry of joy. His enemy had been hit.