The most important event in chapter four of The Outsiders occurs at the park when Johnny and Ponyboy are attacked by a group of Soc boys. The Socs' unofficial leader, Bob, threatens that Ponyboy needs to wash his greasy hair, and the boys proceed to dunk Ponyboy in the fountain. Ponyboy blacks out during the attack, and when he comes to, he realizes that Johnny has stabbed and killed Bob with his switch blade. The attack in the park and Bob's murder changes the direction of the novel, forcing Johnny and Ponyboy to flee their hometown and hide out in the abandoned church in Windrixville.
Chapter four of The Outsiders is the chapter that sets up the rest of the book. Pony and Johnny are in the park hanging out by the fountain. The two boys are talking about nothing too important when the Socs show up. Pony and Johnny realize they can't run away in time, and have to face the Socs on their own. The Socs call Pony and Johnny losers and tell Pony that he needs to wash the grease out of him. They start dunking Pony in the fountain and Pony thinks he is going to drown. All of a sudden it all stops and Pony is relieved until he finds out the reason why it stopped.
Bob, the handsome Soc, was lying there in the moonlight, doubled up and still. A dark pool was growing from him, spreading slowly over the blue white cement. I looked at Johnny's hand. He was clutching the switchblade, and it was dark to the hilt. My stomach gave a violent jump and my blood turned icy.
This is the point when the whole story shifts. Johnny has killed Bob, and Pony has to try to figure out what to do. Pony knows that the police will be against the Greasers, and look at them as just a bunch of punk kids. Johnny did what he had to do to save Pony. We see in this chapter just how close the boys are to each other. They will always stick together and have each other's backs, no matter the consequences.
The most important event in this chapter happens when Johnny and Ponyboy where in the park during the night. The Socs pulled up in a blue mustang and Bob, a Soc, threatens to wash Ponyboy's hair. While Ponyboy suffers in the fountain, Johnny kills Bob. Johnny had to kill him or the Socs would have killed Ponyboy.