In "The Sniper" by Liam O'Flaherty, how and why does the setting develop the protagonist’s character?

The protagonist in this story is the sniper.  He never gets a name.  His antagonist is another sniper, who also doesn't get a name.  In fact, none of the characters in the story get a name.  They all remain completely anonymous.  What this does to the story is that it makes every single person in the story a nameless target.  That's all the sniper sees.  He sees bodies to be shot and killed, not people.  The setting is just about as nameless as the sniper is.  The reader is told the story is taking place in Dublin, but not much else.  No building names for example.  All that we are told is that the sniper is on a roof near the O'Connel Bridge.  The city itself is in ruins.  There is rubble everywhere.  Distant gunfire cracks off from all around.  Machine gun nests are set back waiting for targets of opportunity.  Everything about the setting is cold and emotionless.  Which is exactly what the sniper is.  He's a cold, calculating, emotionless killer.  The setting highlights the sniper and the sniper complements the setting. 

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.