John Steinbeck's Of Mice and Men ends with the death of Lennie at the hands of his best friend, George. Steinbeck has been preparing us for a tragic end since the beginning of the novel. Lennie's trouble in Weed, his petting of the dead mouse, and his killing of the puppy have foreshadowed his killing of Curley's wife.
George's killing of Lennie has been anticipated by Carlson's using the Luger to kill Candy's old dog. Steinbeck, however, has George kill Lennie rather than allowing someone else to kill Lennie, which probably would have happened if the mob of men from the barley farm would have caught him.
The ending is very powerful and poignant. George steels himself to commit what he believes is the ultimate act of compassion to his friend - terminating his life. It is also the death of their beautiful dream of freedom and independence, and thus Steinbeck delivers up sobering ideas on two themes which run strongly through the novel - friendship and dreams.
I have the feeling that "Of Mice and Men" is a fragment of a bigger novel that Steinbeck intended to write but gave up on for some reason. It seemed to promise being a story about the lives of itinerant agricultural workers. One of the things that seems lacking is detailed descriptions of the hard labor of the men and the horses in the fields. There are plenty of horses, but they do nothing but nibble hay, stamp their feet, and jingle their harnesses. The men spend most of their time indoors, either playing cards or talking. Even when they pitch horseshoes outside, we only hear the thuds and clangs.
Whenever a story ends with somebody getting shot, I always suspect that the author had run out of inspiration and just wanted to get rid of the thing so he could go on to something else. It seems significant, but it really isn't: it is just an "effect." It is melodramatic. Perhaps Steinbeck realized that he had bitten off more than he could chew--as frequently happens to creative writers. Perhaps he had to face the fact that he just didn't know enough about the subject to describe it realistically--especially to describe scenes in which gangs of men with teams of horses are working out in the flat California fields. Steinbeck does a beautiful job of describing a little campsite by a river with the mountains in the background. He does an effective job of describing a bunkhouse. Some of his characters seem real--but he could have met them in bar rooms. He didn't have much of a plot to work with. That was another one of his problems. When he wrote The Grapes of Wratha few years later, it was a full-fledged epic, and it had its own natural movement of dispossessed people moving from east to west. Of Mice and Men, by contrast, seems claustrophobic.
I think the question we may be left with at the end of the novel is: Where can we find innocence in this world driven by corrupted cravings?
Lennie was "innocent" if we look only at his intentions. He never meant to hurt anyone. Yet he killed a woman just as he killed small animals - according to his nature. Lennie is not innocent if we consider these actions. Because he craved soft things, he became a killer.
The result of Lennie's lack of control is George's decision to take Lennie's life. To protect Lennie from punishment and to protect other people from Lennie's craven (if unintentionial) harm.
The ending of Steinbeck's Of Mice and Men is in accord with the characteristic naturalism of Steinbeck's novella. Like the poem of Robert Burns from which the title of the work comes, it is an uncaring universe that allows circumstances to occur. No matter their plans, like the little mouse who has built its winter nest, death comes without invitation to Lennie and George. As Steinbeck himself has written, Lennie represents represents not insanity, "but the inarticulate and powerful yearning of all men," a yearning that is up against the forces of society and an indifferent universe. The American Dream dies in the Great Depression; Lennie as the keeper of the dream dies in Of Mice and Men.
he choose to end in that way because he is trying to show that nothing changed on the ranch; especially Carlson. He is still insensitive and does not understand the bond between George and Lennie ( this was the same with Candy and his dog)