A police source has said 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 the arguments centered on missed car payments.

Investigators have focused on suspect William Balfour’s movements on Friday, the day of the murders, as well as his conflicts with Julia, and other members of the family. They are trying to determine whether another person drove Balfour to the West Side after the killings at the Hudsons’ South Side home.

Witnesses said Balfour drove his teal Chrysler to the Hudsons’ block Friday, arriving about 7 a.m. But later the vehicle was discovered by police parked about a mile away outside Robeson High School. Balfour’s girlfriend told police that he was at her West Side home not long after the slayings of Hudson’s mother, Darnell Donerson, and the Oscar-winning actress’ brother, Jason, at their Englewood home, reports The Chicago Tribune.

The body of Hudson’s 7-year-old nephew, Julian King, was discovered Monday morning in the back of Jason Hudson’s Chevy Suburban, parked on a West Side street.

Security video at the South Side high school showed someone parking the Chrysler on Friday, but investigators have not been able to determine the person’s identity from the images. A time stamp on the video showed the car was left there at 12:30 p.m. Friday, but it was unclear whether the stamp was accurate, sources said.

Meanwhile, cell phone records placed Balfour on the West Side at that hour. If the time stamp is accurate, it would suggest another person may have driven the Chrysler from the Hudson home to Robeson, sources said. In any event, Balfour did not use his own car to travel from the Hudson’s Englewood house to his girlfriend’s home near 19th Street and Spaulding Avenue on the West Side, police said.

As detectives continued searching for answers, the Cook County medical examiner’s office released autopsy results Tuesday showing Julian King died of multiple gunshot wounds.

Also on Tuesday, new details surfaced about Balfour’s criminal and personal history.

Records show that Balfour missed a meeting with his parole agent on Friday, the day Hudson’s mother and brother were murdered and her 7-year-old nephew went missing. Reached by phone that afternoon, he told the agent he was “baby-sitting on the West Side of Chicago,” according to the documents, obtained by The Associated Press. The agent said he thought he heard a child in the background during the call.

As reported by TMZ, he isn’t the first Balfour to run afoul of the law. Balfour’s father is currently serving a 30-year prison sentence for murder. His brother served time for drug dealing. And as previously reported, Balfour himself has served time for attempted murder and carjacking.