What is Wes Moore's reason for writing the book The Other Wes Moore?

The coincidence of two men from the same neighborhood in the same city sharing the same name is not extreme. What initially caught the attention of the author is that within a short period, his hometown newspaper, the Baltimore Sun, published an article about him and a series that included the "other Wes Moore." The author had finished his undergraduate education at Johns Hopkins University and been awarded a Rhodes Scholarship to study in England. The young man who shares his name had participated in an armed robbery that resulted in his brother killing off-duty police officer Bruce Prothero.
The vast disparity in their experiences and the future to which they would lead—as the other man, once convicted, would likely be incarcerated forever—would not leave the author alone. The differences that led him down one path and the other man down another are, the author claims, very small. He hopes that his analysis of their two stories will show how alike they are despite their separate lives:

The tragedy is that my story could have been his. Our stories are obviously specific to our two lives, but I hope they will illuminate the crucial inflection points in every life, the sudden moments of decision where our paths diverge and our fates are sealed.