(CNN) -- Chicago, Illinois, police arrested a man Monday in connection with the killing of three relatives of singer-actress Jennifer Hudson, a police spokesman said.
William Balfour, 27, was first detained for questioning on October 24, the day Hudson's mother and brother were found shot to death. Authorities said at the time that they were holding Balfour for an unspecified parole violation.
Hudson's mother, Darnell Donerson, and brother, Jason Hudson, were found shot to death in their South Side Chicago home. The body of her nephew, 7-year-old Julian King, was found three days later in an abandoned SUV on Chicago's West Side.
Police later found a handgun near the vehicle.
Detectives served arrest warrants on Balfour on Monday afternoon, said Chicago police spokeswoman Monique Bond.
Balfour was transferred from the Statesville Correctional Center to the custody of detectives in the case, she said, and he is awaiting formal charges on three counts of murder.
Balfour is the estranged husband of the singer's sister, Julia Hudson, and the stepfather of Julian King.
According to the Illinois Department of Corrections, Balfour spent nearly seven years in prison for attempted murder, vehicular hijacking and possessing a stolen vehicle. He was free on parole at the time of the shootings.
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 the singing competition "American Idol" in 2004, becoming one of the top seven contestants before being eliminated from the contest.
Michele Davis-Balfour, Balfour's mother, passionately defended her son Monday to reporters. She said that at least one of the witnesses that police used to build a case against Balfour was lying.
"My son did not do this. I am sick of this. They need to focus on somebody else," Davis-Balfour said.
She said Balfour has an alibi: He was with one of his three girlfriends the night of the slaying.
"He was with Diana that night and with Kate in the morning," she said.
Balfour's attorney Josh Kutnick also said Balfour has told him that he did not commit the crimes.
"He believes when the evidence comes out, he will be found not guilty," Kutnick said.
CNN's Susan Roesgen contributed to this report.