Although your question is not very specific, one of the first major acts of violence in Susan E. Hinton's novel, That Was Then, This Is Now, takes place in Chapter 3. Bryon has borrowed Charlie's car to take Cathy to the school dance. While there, Bryon runs into Mark and his friend Ponyboy Curtis (of The Outsiders) as well as his old girlfriend, Angela Shepard. While Bryon and Cathy are inside, Ponyboy rushes in to announce that "Mark's hurt!" Mark is unconscious, having had a bottle broken on his head. Ponyboy explains that the bottle was meant for him, and Bryon determines that Angela had put the assailant up to it to pay back Ponyboy for his lack of interest in her. Bryon vows revenge against Angela, setting off a chain of violence that includes the death of Charlie and Bryon's severe beating by Angela's brothers (Tim and Curly Shepard, also of The Outsiders).