Who is looking to kill rusty-James?

In the novel "Rumble Fish" by S.E. Hinton, Rusty-James is pursued by a character named Biff, who is seeking revenge for a previous encounter. Biff's vendetta stems from a fight with Rusty-James, leading to a desire to confront him again. The tension between them highlights the themes of violence and the consequences of gang life in the story.