In many of his writings, Orwell views imperialism as a mechanism for economic power, for enabling the Western nations to have a higher standard of living by exploiting underdeveloped countries. However, in "Shooting an Elephant" he goes further and develops the theme of imperialism as a means by which the industrialized countries control their own populations.
In the narrative Orwell makes it clear that the British are hated by the Burmese, but also that Orwell, a British policeman, has no love either for the "native" population, including the seemingly benign Buddhist priests. It is impossible even for a policeman or a soldier having the best of intentions, and the most liberal mindset, to feel favorable to people who are constantly jeering him and taunting him on the street. The elephant incident brings these emotions of mutual dislike to a head.
Though the "natives" obviously resent the British presence, they also seem to have adopted the attitude that since the white man has put himself in charge, he is the one who can and must take care of all problems. When the elephant goes "must," running wild and causing havoc (including killing a laborer by stamping him into the ground), Orwell has no choice but to take action. He repeats over and over that "I did not want to kill the elephant," for he realizes that the attack of "must" is already passing. The elephant will soon become harmless again, and can be recaptured by its owner, with no further death or damage. Yet a crowd has gathered, urging him to neutralize the elephant, as it were. Because he's the white man, he is expected to act, despite his not wanting to, and despite the fact that the crowd of Burmese are not capable of forcing him to. It is to save face that Orwell must pull the trigger and kill the elephant.
It is at this point, as he holds the rifle, that Orwell has an epiphany about why imperialist countries act as they do. He has been put in a position—that of being forced to do something unnecessary and against his own moral code—where he lacks freedom, though as the white man he's supposed to be the one in charge. "When the white man turns tyrant, it is his own freedom he destroys....He becomes a hollow, posing dummy, the conventionalized figure of a sahib." In other words, both conquered and conqueror have become enchained as a result of the imperialist government's power-lust. The difficulty of killing the elephant, when Orwell has to pour shot after shot into him, is symbolic of the dysfunctionality and cruelty of the whole situation. When the elephant is felled, a shout of triumph goes up from the crowd, probably partly because they have at least unconsciously realized that this is a victory over not just the elephant, but over the British invaders as well.