Chicago police have linked a gun found last week in a vacant lot to the killings of Oscar-winning actress and singer Jennifer Hudson's mother, brother and 7-year-old nephew.
Police found the .45 caliber gun in a vacant lot about a block from where the body of Hudson's nephew, Julian King, was discovered Monday morning, ABC News Chicago affiliate WLS-TV reported.
Forensic testing on the gun showed it to be the same weapon used to kill all three people, police said.
Police have not named a suspect in the killings, but Chicago Police Department Superintendent Jody Weis said that identifying the weapon used in the crimes was a positive step.
"We've still got a lot more to do," said Supt. Jody Weis, Chicago Police Department. "There's still a lot more forensic examination to do. Right now, we're extraordinarily pleased and satisfied that the weapon has been identified as the weapon that has been used in the homicides. And there's still more work to do which we are doing at this time."
The Bureau of Alcohol, Tobacco and Firearms traced the gun to the original owner in Michigan, who had reported it stolen, WLS-TV reported.
"Recovering the weapon was a good sign. It gives us some additional clues. We're going to keep running them down. Like I mentioned before, I am extremely confident that this case will be solved," Weis said Thursday, the day after a police trainee found the gun.
Though he has not officially been called a suspect, William Balfour, the estranged husband of Jennifer Hudson's sister, is a person of interest in the case, police said.
Balfour, 27, has reportedly refused to take a polygraph test and has stopped cooperating with investigators. He is being held on a parole violation.
Julian King's body was found Monday in the back seat of a white Chevrolet Suburban that police had been looking for since Oct. 24, when he went missing and Hudson's mother and brother were found shot to death in their home on Chicago's South Side.
The vehicle was found about 10 miles southeast of the Hudson family home, and police said that the boy had been shot multiple times.
"We're just sad. We're going through this stage where we're just sad and in shock," Hudson's aunt, Dorothy Hudson, told The Associated Press Monday. She and her husband, John, own a Chicago funeral home that plans to handle arrangements for the family.
Hudson's mother, Darnell Donerson, 57, was found dead on the living room floor by her other daughter, Julia Hudson. Officers later discovered Hudson's brother, Jason Hudson, 29, in a bedroom.
Police say until they find evidence to the contrary, they believe one person is responsible for all the killings.
Records from the Illinois Department of Corrections show Balfour is on parole and spent nearly seven years in prison for attempted murder, vehicular hijacking and possessing a stolen vehicle.
According to their marriage license, Balfour and Julia Hudson were married on Nov. 14, 2006. Neighbors and his family members said the couple had been separated for about a year.
Balfour's mother, Michelle Davis Balfour, said Donerson had ordered Balfour to move out of the family's home last winter, according to local reports.
According to neighbor Bernice Russell, there was "a lot of tension" between the pair, and Russell overheard another neighbor say that Balfour had threatened to kidnap Julia's son a couple weeks ago.
Russell said as far as she knew, Balfour was living with his girlfriend, with whom he is expecting a child. The Tribune reported that police had interviewed her and that her account contradicted Balfour's alibi the day of the killings.
Russell's husband Joe said he had been "very dismayed" by the slayings. "I've never seen this kind of violence before," he said about his neighborhood of 17 years. "They were nice people."
The tragic events come just before Jennifer Hudson was scheduled to embark on a world tour today to promote her self-titled debut album with its chart-topping single, "Spotlight."
Hudson, whose star had been on the rise after she was ousted on Season 3 of "American Idol," was featured in the summer blockbuster "Sex and the City" and stars in the film "The Secret Life of Bees."
In 2007, she hit superstardom with her debut film role in "Dreamgirls," earning a best supporting actress Academy Award for her role as rising singer turned down-and-out single mother Efie White -- a role Hudson said she always wanted to play.
The singer also recently announced her engagement to David Otunga, best known for his stint on VH1's reality show "I Love New York."
ABCNews.com's Luchina Fisher, Imaeyen Ibanga and Scott Michels contributed to this report.