In the second chapter of John Steinbeck's novel Of Mice and Men, George and Lennie have arrived at the ranch where they will live and work, and are introducing themselves to their fellow ranch-hands. One of their new colleagues and friends, Slim, is revealed to be the owner of a female dog that has recently delivered a litter of puppies. Hearing this, Lennie, the sensitive giant with the mentality of a small child, begins agitating for one of the puppies. Lennie has already, it is made clear in the opening chapter, demonstrated a facility for accidentally killing small, furry animals like mice, much to the consternation of his smaller, smarter friend George. Lennie is given one of the puppies from Slim's litter, and quickly falls in love with the small delicate animal. In the fifth chapter of Steinbeck's novel, Lennie is revealed as having accidentally killed his puppy. Steinbeck's narrator describes the setting as follows:

"Only Lennie was in the barn, and Lennie sat in the hay beside a packing case under a manger in the end of the barn that had not been filled with hay. Lennie sat in the hay and looked at a little dead puppy that lay in front of him. Lennie looked at it for a long time, and then he put out his huge hand and stroked it, stroked it clear from one end to the other. And Lennie said softly to the puppy, “Why do you got to get killed? You ain’t so little as mice. I didn’t bounce you hard.” 

Lennie is revealed as having killed the puppy in the fifth chapter, with setting being the inside of the barn.

Lennie kills the puppy in chapter 5. This chapter, as well as the other four, foreshadow the death of Curley's wife.

As far as the setting goes, the opening chapter gives a great description of the landscape. The reader also learns that George and Lennie are in Salinas, California, and they are going to the Hooper Ranch to work.

Look in the first part of Chapter Five