Rapper Chief Keef's stepbrother has been shot dead in his native Chicago, Illinois.

Ulysses 'Chris' Gissendanner Iii, who also went by the name YPN Boomtown, was gunned down in a car on the Far South Side after visiting his uncle last week (02Jan13). He passed away at Roseland Hospital, aged 19.

Chief Keef's father Alfonso Cozart was stepfather to Gissendanner. Authorities do not suspect he was killed due to his connection with the hip-hop star.

Cozart, who no longer speaks to his famous 17-year-old son, tells news website DNAInfo.com, "He just graduated high school, and was in college and had a job. He was a positive person."

Aspiring rapper Gissendanner's manager is just as devastated, adding: "He rapped about struggling and what he was going to do. He was going to make it big. We were going to make it big."

Chief Keef, born Keith Cozart, has yet to publicly speak out about the tragedy, but according to the slain teen's mother, Aridecy Tate, the boys were close growing up - although they drifted apart over the last few years.

She explains, "They were brothers. They used to play together, coming over to our house, getting haircuts together. A lot of brotherly stuff."