What happened when Bob was murdered in "The Outsiders"?
This occurs on the night Ponyboy decides to run away from home, after falling asleep in a lot with Johnny. He comes home to Darry's anger, and seeks Johnny out to escape. they end up in a park around 2 in the morning. They are jumped by a group of Socs (the same ones who jumped Johnny earlier in the story, prompting him to begin carrying a knife). Bob begins pushing Ponyboy's head into a fountain, to the point of him blacking out. Fearing his friend will die, Johnny demonstrates the fierce loyalty and survival instincts of the greasers by stabbing Bob. When Ponyboy comes to, he finds Johnny sitting on the ground next to Bob's body. They then decide to actually run away, ending up in the abandoned church.
This episode highlights the social differences amongst the 2 groups. Bob can essentially torture the greasers with impunity, while Johnny must run for his life, knowing that no greaser would get a fair trial. It shows that everyone has a breaking point, and most view Johnny as having done the right thing in self-defense.