All the deaths in The Great Gatsby occur in the last few chapters of the novel. First, in chapter seven, Myrtle, Tom's married lover, gets hit by Daisy, who is driving Gatsby's yellow sports car. Daisy and Gatsby flee the scene and leave Myrtle dead in the road. When Tom learns of Myrtle's death and hears that a yellow car hit her, he assumes that Gatsby was the driver, and this angers him immensely.
Later, Gatsby tells Nick about the accident and accidentally lets it slip that Daisy was driving "the death car." However, he says he will take the blame, sacrificing himself for Daisy. She, on the other hand, is not as concerned about Gatsby as she is about herself, and she cowardly runs from her crime and back into the arms of her husband.
While all this is happening, George, Myrtle's husband, is disconsolate and demands justice for Myrtle. He realizes that Tom knows who the owner of the yellow car is, and he sets out to find the killer. At the end of chapter eight, Gatsby is floating on an air mattress in his pool, waiting for Daisy to call. George, believing Gatsby to be his wife's murderer, shoots and kills him and then turns the gun on himself.
All in all, three people are killed in The Great Gatsby: Myrtle is killed by Daisy, Gatsby is killed by George, and George kills himslef.