A suspect in the slayings of Oscar winner Jennifer Hudson's mother and brother was transferred to state custody Sunday for violating his parole after he stopped cooperating with police investigating the killings and the disappearance of Hudson's nephew, authorities and law-enforcement sources said.

Also on Sunday, Hudson offered a $100,000 reward for the return of her nephew, Julian King, 7, who has been missing since Hudson's family members were discovered shot to death in their Englewood home Friday.

"Jennifer and her family appreciate the enormous amount of love, support and prayers they have received while she and her family try to cope with this tragedy and continue the search for Julian," Hudson's publicist, Lisa Kasteler, said in a statement announcing the reward. Information about the boy should be directed to Chicago detectives, Kasteler said.

Police and the FBI continued the search for Julian, who they say may have been taken in a 1994 white Chevrolet Suburban with Illinois license plate X584859. On Sunday, police and volunteers fanned out into Englewood and surrounding neighborhoods, handing out fliers with a photograph of the boy and description of the vehicle.

William Balfour, 27, the estranged husband of Hudson's sister Julia, was questioned at the Wentworth Area police station beginning Friday night and denied involvement in the killings or the disappearance of the boy, law-enforcement sources said. But at some point, Balfour stopped talking to authorities, the sources said.

On Sunday morning, Balfour was transferred to a state facility after officials said he violated conditions of parole for a 1999 conviction for attempted murder.

Chicago police this weekend declined to call Balfour a suspect, saying they have only been interviewing him. He has not been charged in the slayings.

But an alert on Friday about the missing boy named Balfour a suspect. And on Sunday, Illinois Department of Corrections spokeswoman Januari Smith said Balfour violated his parole because he is a suspect in the slayings and the boy's disappearance. Balfour could be held in state custody until he goes before the Illinois Prisoner Review Board, which will determine whether he has violated parole. That could take weeks, Smith said.

The homicide investigation remains focused on Balfour, sources said. Balfour's alibi the day of the killings has been contradicted by his girlfriend, law-enforcement sources said. Balfour was arrested at the woman's Southwest Side home Friday night. Balfour and Julia Hudson had been separated for some time, his family members said. A family friend said Balfour recently had threatened to take Julian away.

A family member of the girlfriend's said police have interviewed her. Police also tracked Balfour's whereabouts Friday through his cell phone, sources said.

Balfour's mother, Michele, said her son is not responsible for the killings or Julian's disappearance, adding that he was with his girlfriend that day.

"How are they doing this to him? This is because they're stuck in an investigation," his mother said Sunday.

The killings occurred about 9 a.m. Friday when a gunman shot through the front door of Darnell Donerson's home, striking Jason Hudson, 29, first before continuing through the door and shooting Donerson, 57, sources said.

Accustomed to gunfire, neighbors did not call police.

A family member found Donerson's body about 3 p.m. Friday and called authorities, who then found Jason Hudson's body in the home. But Julian was missing.

Police issued an Amber Alert for the boy and Jason Hudson's white Suburban. The FBI was brought in Saturday on the chance the boy might have been taken out of state. Police officers circled back to the home Saturday, searching it again in case the boy was hiding, but to no avail.

The Hudson family issued a statement Sunday on Jennifer Hudson's MySpace page.

"Thank you all for your prayers and your calls. Please keep praying for our family and that we get Julian King back home safely. If anyone has any information about his whereabouts please contact the authorities immediately. Here is a picture of Julian and what he was last seen wearing. Once again thank you all for being there for us through this tough time. Sincerely, The Hudson Family."

The family home in the 7000 block of South Yale Avenue has become an epicenter of grief for Chicagoans, who trickled by all weekend to pay tribute. Jennifer Hudson rocketed to stardom after appearing on "American Idol," then outshining co-stars in the movie "Dreamgirls." Longtime Englewood residents said the woman remained true to her roots, returning often to spend time with family, with whom she remained close.