BX is Shaka's roomie at Oaks after Shaka gets out of solitary. He's also in the Melanics, and Shaka and BX become like brothers. But they have more in common than just religion. BX works in the law library in the prison, and so does Shaka.
He acts as a bit of a mentor-figure for Shaka. Although BX's own sentence is fifty-two to seventy-five years, he helps Shaka keep on track to be released by reminding him how much he needs to tell his story to help their community.
They both get transferred to Carson City around the same time, and they collaborate to organize study groups and other things for the Melanic Brotherhood there. Carson City turns out to have a huge amount of racial tension (Black inmates are frequently bullied by prison guards), so BX and Shaka organize to help inmates use the prison grievance system to try to make things better.
On the less positive side, when Shaka is nearing the end of his prison sentence and is transferred to a new place, BX writes and asks him to get revenge on a guy there who molested his niece and son. Shaka has moved on from violence as a way to solve problems, but he really cares about BX. Shaka winds up hiring someone else to stab the guy. That's the last violent thing Shaka participates in while incarcerated.