While somewhat surprising, the moral consciousness that emerges in the poorly educated son of a sharecropper that motivates him to inform the de Spains that their barn will burn is more moving than it is shocking to the reader. For, throughout the narrative of "Barn Burning," Colonel Sartoris Snopes, or Sarty as he is called, shows evidence of intelligence, being both very observant of details around him, and pensive and analytical.
Having been taught to give unthinking loyalty to his pyromaniac father, Sarty finds himself in morally compromising situations which only lead to other unhappy circumstances. For instance, in the exposition of the story when Sarty is in the general store as his father faces the judge, he perceives the man Harris whose barn his father burned as "Enemy, enemy!" But, later, his father strikes him, "hard but without heat, exactly as he had struck the two mules" and tells him, "You were fixing to tell him [the judge]." This detached behavior of his father, who forces the family to become transients, disturbs Sarty. Sarty witnesses, too, the "incorrigible idle inertia" of his "bovine" sisters who seem degenerate and worthless.
When Sarty finds himself again in similar general store and courtroom as his father sues his landlord for charging him ten bushels of corn for the damage to a French rug, he finds himself running for oil for his father who plans to burn the barn of this landlord:
Then he was moving, running, ...toward the stable: this the old habit, the old blood which he had not been permitted to choose for himself, which had been bequeathed him willy nilly and which had run for so long....I could keep on, he thought. I could run on and on and never look back, never need to see his face again.
It is at this point that Sarty begins to question how far family loyalty should extend, or if moral ethics transcend this loyalty. And, so, he wrestles free of his aunt's hold and runs to tell M. de Spain that his father is going to burn his barn. It is not shocking, then, that de Spain shoots Abner Snopes who pours oil upon the barn in order to light it; however, Sarty is devastated, calling out, "Pap! Pap! " Nevertheless, he wakes the next day and departs without taking "a look back" as he has acquired a burgeoning social consciousness that will lead him to become a man.