In the story, the narrator shoots the elephant because the crowd demands he do so. The beast had run wild through a bazaar, trampling one man to death, and causing the Burmese people to demand that it be put to death. The man pressured to do this is the narrator, who is a sahib, or British imperial policeman, in Burma. So in killing the elephant, he does what the crowd demands of him and fulfills the role of a British imperialist. However, the narrator does not want to commit the act. When he encounters the elephant, it is peacefully eating grass, and no longer represents a threat. But Orwell's narrator feels that he must go through with it:

A sahib has got to act like a sahib; he has got to appear resolute, to know his own mind and do definite things. To come all that way, rifle in hand, with two thousand people marching at my heels, and then to trail feebly away, having done nothing – no, that was impossible. The crowd would laugh at me. And my whole life, every white man's life in the East, was one long struggle not to be laughed at.

This is a very telling quote, one that Orwell uses to illustrate the contradictions and immoralities inherent in empire. The crowd demands that the narrator carry out this act, which is contrary to his conscience. He views it as arbitrary and bloodthirsty, which, he recognizes, is exactly how the crowd expects him to behave. He does what he does in no small part to avoid looking like a fool. Orwell himself was a sahib in Burma, so the short story is to some extent autobiographical, and the shooting of the elephant in the story illustrates the moral ambiguities, if not complete immorality, of empire.