He has Lennie imagine the farm that they are going to get together. That farm has become a symbol of all that is good in life, and George adds one additional part to this familiar story. He tells Lennie that this farm is going to be a place where no one will ever be mean to anyone else... ever. The farm has become their personal heaven. If you look at the last chapter, there are several images that are very reminiscent of Psalm 23:4.
He distracted him by comforting him and telling him their dream he tells Lennie to look ahead at the beautiful sunset and scenery which can be compared to the Garden of Eden in the bible. Then he quickly and calmy pulls the trigger. This can be compared to the killing of Candy's dog.