* He wasn't present for the fight: Ponyboy is with Johnny and Dallas when Bob is killed. He's across the street, observing from a distance, and doesn't actually witness the fight.
* He blames himself for being there: Ponyboy feels responsible for the situation because he was there with Johnny and Dallas, and he blames himself for being a greaser. However, he doesn't believe he directly participated in Bob's death.
* He feels guilt and confusion: Ponyboy is overwhelmed with guilt and confusion after the events. He feels responsible for Bob's death because he was part of the group that was involved, but he doesn't believe he physically killed him.
* The story is told from his perspective: The novel is narrated by Ponyboy, and we experience the events through his eyes. His internal thoughts and feelings, including his guilt and confusion, are what we are shown.
It's important to remember that Ponyboy is a young boy experiencing a traumatic event. His feelings of guilt and responsibility are natural, even though he didn't directly kill Bob.