Who killed Darius Drake?

Arthur Bash is the school thug-for-hire (paid in candy bars), mostly because he just looks the part, so when orphan Darius Drake offers him three candy bars to accompany him to the run-down Stompanado Housing Complex, and just look menacing, he agrees--and soon finds himself deep in a mystery involving Darius' estranged grandfather, the lost Dunbar Diamonds, and the villainous Jasper Jones.