CHICAGO, Illinois (CNN) -- The body found inside an SUV Monday morning has been confirmed to be Oscar-winning actress Jennifer Hudson's 7-year-old nephew, a top FBI official said.
The white SUV where the child's body was found is taken away to be examined by investigators.
The medical examiner positively identified the body found in the white Chevrolet Suburban as Julian King, Chicago Police Superintendent Jody Weis said Monday afternoon.
Julian had been shot to death, said police spokeswoman Monique Bond.
Police are collecting evidence from the Suburban and reviewing surveillance tapes from all over the city as the investigation continues, Weis told reporters.
"There's a lot of work to be done. We'll be sure we go through this thoroughly," he said.
Asked about possible motives, Weis said, "We don't know what the motive really was at this time. But, clearly you have people who do know each other, so it wasn't a case of a stranger-type homicide."
Earlier Monday Deputy Chief Cmdr. Wayne Gulliford said police found the body inside a parked white Chevy Suburban with a license plate matching the description in the child's Amber Alert, after responding to "a call about a suspicious auto" on Chicago's West Side at approximately 7 a.m.
He had no details on the body, pending the medical examiner's report.
Julian has been missing since Hudson's mother and brother were found dead in their home Friday. Watch police say they've ID'd the body »
Over the weekend, Hudson offered a $100,000 reward for the safe return of her nephew.
"Please keep praying for our family and that we get Julian King back home safely," Hudson said in a posting on her MySpace page Sunday. "If anyone has any information about his whereabouts please contact the authorities immediately."
Hudson also posted two pictures of her nephew wearing the brown-and-orange striped polo shirt he was wearing when he was last seen.
Earlier, Hudson viewed the bodies of her mother, Darnell Donerson, and brother, Jason Hudson, the Cook County medical examiner's office told CNN on Sunday. They were found shot to death Friday in their South Side Chicago home. Watch the latest on the Hudson case »
Julian's stepfather, William Balfour, was detained over the weekend for questioning in connection with the case, a police spokesperson told CNN. He was subsequently transferred to prison on a parole violation charge, the spokesperson said.
No charges had been filed against anyone in connection with the murders.
According to the Illinois Department of Corrections, Balfour, 27, spent nearly seven years in prison for attempted murder, vehicular hijacking and possessing a stolen vehicle.
Chicago news station WLS reported Saturday that Julian was not with Balfour when he was detained.
Hudson's sister, Julia Balfour, made an emotional appeal Saturday for the safe return of her son.
"My greatest fear has already happened, my greatest hope is for having my child. I just want my son," Julia Balfour said. "That's all I have to say. Just let my baby go."
William Balfour's mother, Michele Davis-Balfour, also urged the public to focus on finding Julian and said her son had nothing to do with the slayings.
"Out of no means did my son do this. This heinous crime to this family is unbelievable. It's unbearable," Davis-Balfour told WLS. Watch Davis-Balfour's emotional appeal »
Deputy Police Chief Joseph Patterson said the bodies of Hudson's mother and brother were found about 3 p.m. Friday, when a relative arrived and found the body of a woman on the living room floor. The relative backed out of the house and called police, Patterson said. Authorities found a man shot to death in a bedroom.
The Cook County medical examiner's office said Saturday that Donerson and Jason Hudson suffered multiple gunshot wounds and ruled the deaths homicides.
Neighbors reported hearing gunshots earlier Friday, Patterson said. Authorities found no signs of forced entry to the home and were not sure whether other items were missing. Watch the scene outside the house »
"You've got two people who were killed inside a home. That alone will produce a great deal of evidence," Chicago Police Superintendent Jody Weis said of forensic evidence at the crime scene.
Hudson won a Best Supporting Actress Oscar for her portrayal of Effie in the film version of the Broadway musical "Dreamgirls." She competed on the third season of "American Idol" in 2004, making it to the top seven contestants before being eliminated from the contest.
CNN's Susan Roesgen and Kevin Bohn contributed to this report.