In "The Sniper" by Liam O'Flaherty, how do the conflicts experienced by the main character reveal his personality?

The Republican sniper, who is the protagonist of Liam O'Flaherty's short story, is at once cold and calculating, while also revealing profound guilt and regret as he battles an enemy sniper on the rooftops of Dublin during the Irish Civil War. At first, the sniper displays a fearless, calculating approach to his job. He is described as a "fanatic" who was used to "looking at death." He kills, seemingly without remorse, the old woman and the armored car commander. When he is wounded by the opposition sniper, he acts without panic, treating his wound and devising a plan to rid himself of his enemy. He tricks the Free State sniper into revealing himself by faking his own death. Then, he uses his pistol to coldly shoot his opponent. O'Flaherty even notes that the Republican sniper did so with a smile. Afterward, however, the shock and senselessness of his actions overwhelm the sniper as he temporarily breaks down into grief and madness:

The sniper looked at his enemy falling and he shuddered. The lust of battle died in him. He became bitten by remorse. The sweat stood out in beads on his forehead. 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.

While being initially portrayed as heartless and machine-like, the sniper is given very human qualities in this paragraph. He understands the cruel nature of war and how it has impacted his life. Even before it is revealed that he had killed his own brother, the reader may decide that the sniper will always carry the figurative scars of warfare. After the final line of the story, it will be impossible for him to ever forget what he has done.