What specific moment is the climax of "The Sniper" by Liam O'Flaherty?

One could consider the climax of "The Sniper" the moment when the Republican sniper successfully tricks the opposing sniper and kills him in one shot. The moment that the enemy sniper wounds the Republican sniper is considered the rising action, which leads to the climax. The Republican sniper ends up removing his helmet, placing it over the muzzle of his rifle, and slowly raising the helmet from behind the parapet so that the enemy sniper can see it. The enemy sniper then shoots the helmet off of the rifle and assumes that he killed the Republican sniper. The climax takes place when the Republican sniper peeks above the parapet undetected and shoots the unsuspecting enemy sniper. The events that transpire following the climax are considered the falling action, and the story concludes when the Republican sniper discovers that the enemy sniper he killed was his brother.

The climax is the highest point of interest in the plot of a piece of literature. In Liam O'Flaherty's "The Sniper," the plot revolves around the actions of a Republican sniper on a Dublin rooftop during the Irish Civil War. After revealing himself to the enemy by killing an old woman and armored car commander in the street below, the sniper is confronted with an enemy sniper who is out to kill him. The climax of the story comes when the Republican sniper kills his opponent after tricking him by pretending to be dead and dropping his rifle into the street. When his adversary comes into the open, the Republican sniper shoots him with his pistol. Everything after this point in the story must be considered the falling action and resolution, in which the sniper discovers the man he killed was his brother.