In the short story "Of Mice and Men" Lennie, a strong man with mental disabilities and his guardian George go to work at a ranch. While at the ranch they meet an old man named Candy. Candy is alone and used up. He has an injured hand and can no longer do field work. He has an old dog that is in bad shape. The dog is a symbol that represents several things in the story, Candy's own state as not being worth much to society anymore, and a foreshadowing of what will happen to Lennie. When Slim tells Candy that the dog needs to be put out of his misery he does not want to do it. Slim makes the determination that it needs to be done. Candy is very unhappy that it has been decided for him that his dog will be killed.
A ranch hand named Carson takes the dog out and shoots it. Candy is left feeling guilty and states "I should have done it myself." Again foreshadowing is used to better help the reader understand why in the end of the story George chooses to shoot Lennie rather than let the others put him to death. He is doing for Lennie that which Candy could not do for his dog.
In the novella, Of Mice and Men, Candy's dog is shot by Carlson. Carlson tells Candy that the dog smells, has no teeth, is blind--in other words, the dog is too old and isn't good for anything anymore. Carlson offers to shoot the dog for Candy. He takes the dog out a ways from the ranch house and shoots him. Later, Candy regrets letting Carlson shoot the dog. He tells George that he himself should have done it.
In the short story "Of Mice and Men" Lennie goes into the stable and sees the puppies. Lennie is very excited about the puppies that are owned by Slim. Slim is their field boss. Lennie is attracted to things that are soft to the touch. He likes to pet animals because of their fur.
Slim is impressed by Lennie being such a hard worker, despite Lennie's mental disabilities, and also by George's devotion to Lennie. When he shows the puppies to Lennie and sees how much Lennie enjoys them, he promises him one. Lennie sneaks back to pet the puppies but like he has always done in the past with small animals, he accidentally pets them too hard killing them. He hides them under the hay so that George will not find them because he is afraid George will get made at him.
Lennie is the one who kills the puppies.