Why does Myers include the flashback to when Steve was twelve years old towards the beginning of the novel?

The flashback which takes place early in the novel shows twelve-year-old Steve Harmon walking with his friend Tony in a neighborhood park. Tony picks up a stone and throws it off of a lamppost. Steve then throws a rock which accidently hits a woman after the rock sails past the lamppost. A tough man who was walking next to her turns around, looks at the two boys, and asks who threw the rock. Steve yells, "Tony! Run!" (Myers 47). The guy then punches Tony as Steve backs away. After the woman pulls the man away, Tony says to Steve, "I didn't throw that rock. You threw it" (Myers 47). Steve responds by saying, "I didn't say you threw it. I just said "Run." You should've run" (Myers 47). Steve's flashback gives the audience insight into Steve's personality. Steve was okay letting Tony take the blame and punishment for something he did. Steve also justifies not taking responsibility by saying that he told Tony to run. Steve has a tendency to make bad choices and tries to justify his wrong actions instead of taking responsibility for them. Steve does the same thing in his attempt to distance himself from his participation in the plot to rob the drugstore during the trial.