In, "Of Mice and Men," two simple men Geoge and Lennie are camping out for a night in the woods after running from thier old ranch and looking for a new one. George and Lennie have a dream of one day owning thier own ranch, this is symbolic of the American Dream. This shows that the most simple people strive for their dreams.
Tell me about the rabbits George!
In this scene Candy's dog is getting too old to live on the farm and Carlson wants him gone, and shoots the dog instead of Candy. This foreshadows Lennie's death later on in the book, and shows that Candy and his dog are foils for George and Lennie. This shows how friends need to make tough decisions for the betterment of eachother.
Curley's Wife finds Lennie in the barn and finds a puppy Lennie accidentally killed. She tries to comfort Lennie, but he gets too agressive and accidentally breaks her neck as well. This is the climax if the story. There is no going back from here. This shows how dreams are destined to fail before they even begin by Lennie ruining their dream of owning a ranch.
George finds Lennie after he fled from the farm in the spot where they camped out in the beginning of the book, and he shoots Lennie so the guys from the farm won't hurt him. This is like when Camdy's dog got shot, but this time George is taking matters into his own hands. This scene shows the fragileness of plans and how they are boound to fail.