Julian King, the 7-year-old nephew of Jennifer Hudson, died of multiple gunshot wounds, Chicago's Cook County medical examiner's office said Tuesday.
His death has been ruled a homicide.
Cook County spokesman Sean Howard declined to say where the child suffered wounds or how long he had been dead, citing an ongoing Chicago police investigation, according to The Associated Press.
The announcement follows an autopsy on Julian's body, which was found in the back of an SUV three days after Hudson's mother and brother were shot to death.
Chicago's police chief Jody Weis is confident "we'll have some evidence that will link us to the killer," according to the AP.
While no one has been charged in the slayings, police are eyeing William Balfour - Julia's 27-year-old ex-husband - as a person of interest.
Citing a police source, the Chicago Tribune is reporting that the motive in the killings could be related to ongoing disputes between the suspect and his estranged wife, Julia Hudson, and her family.
One of those disputes was over unpaid car payments, the paper reports.