Answer:
Ponyboy was at the scene of the murder and helped Johnny flee. in the chapter while looking at Bob's picture in the yearbook he states, "I could begin to see the person we had killed.",which goes back to his current mental state. In his current mental state he is assuming the responsibility of Bob's death and is in denial of Johnny having died also, so as a methods of dealing with both of these deaths he denies Johnny had killed Bob and assumes responsibility for it.
Step-by-step explanation: