In this mission you have defeated the 3 ballas (as in mission 3,"Smoked"). Take the Ballas Drivers License. You then find out that the Balla that shot CJ's mom happens to be "Derrick Harris" a former Balla OG. The license also displays Derricks Address. Go to Derricks house and you find his Step brother there. He is very angry. Defeat him and drive back to Ganton as safely as possible.