Steinbeck's use of foreshadowing makes the ending of Of Mice & Men seem inevitable and because of this, even the smallest details are important because they foretell what's going to happen next. Lennie's death is foreshadowed by the death of Candy's dog. There are a lot of similarities between these two deaths.
Two shootings took place in Steinbeck's novel Of Mice & Men. First, Candy's dog is killed then at the end of the book Lennie is killed. These shootings have a lot in common. To start both the dog and Lennie were shot by the same gun, a luger. The dog was shot by Carlson and Lennie was shot by George. Both, Lennie and the dog were shot in the back of the head. Both of the victims' friends reacted the same, they both seemed mesmerized and bemused about what had happened. The dog's shooting foreshadowed Lennie's death.
George never really liked having Lennie around him because he could never do anything without being asked stupid questions by Lennie. George never ended up getting paid for his hard work on ranches because of Lennie. That could have been a reason for George shooting Lennie, it partly was, but when Candy said "I ought to of shot that dog myself, George. I shouldn't ought to of let no stranger shoot my dog." George reacts about this and kills Lennie instead of having Curley do it. In spite of everything that George disliked about Lennie, deep down in his heart George actually loved him.
As the drama of the book adds up the ending seems to get both, more surprising and more predictable. After reading Chapters 1 to 5, a reader might think that he knows what to expect in the ending of the book but is caught by surprise when he concludes reading it.