Formal charges were filed today against the man authorities say killed three members of Oscar-winning actor Jennifer Hudson's family.

William Balfour, 27, who had been Chicago police's lone suspect, was charged with three counts of first-degree murder and one count of home invasion and is scheduled to appear for a bond hearing tomorrow, according to the Cook county, Illinois, state's attorney's office.

Police had worked slowly and methodically, hoping to amass physical evidence against the estranged husband of Hudson's sister, taking time afforded them when Balfour was held for violating his parole. But the case against him is largely circumstantial, according to sources.

There are witnesses who say they saw Balfour at the family's home on the day of the slayings, cell phone tower records that tracked his movements, and a girlfriend who says Balfour confessed and that she saw him with a gun that matched the murder weapon.

The motive, the sources say, was an ongoing domestic squabble among Balfour; his estranged wife, Julia Hudson; and Hudson's family members.

Family members told police that Balfour, paroled for an attempted murder in 2006, had threatened his estranged wife before and was thrown out of the family home, according to law enforcement sources.

Yesterday, two days before Balfour was set to appear before the parole board again - and possibly be freed - police arrested him on a warrant for murder.