In the book, Bob Sheldon is the Soc who dies, and it is Johnny Cade who kills him in self-defense.
This event has a major impact on the story, as Johnny goes on the run and eventually dies in a tragic fire while saving children.
Remember, the Outsiders focuses on the conflict between the Greasers and the Socs, and while violence is a key theme, the novel is ultimately about the struggle for understanding and acceptance between these two groups.