Oak Lawn Murder-Suicide: 4 Killed In Shootings, Fire In Chicago Suburb

Police say a 36-year-old man was responsible for fatally shooting his 5-year-old nephew and both of his parents, setting their house ablaze and taking his own life early Wednesday morning in the Chicago suburb of Oak Lawn.

An off-duty fire official responding to reports of a fire at the home around 5 a.m. witnessed a man later identified as John Conta Jr. fatally shoot himself with a shotgun in the garage attached to the home in the 9800 block of South 51st Avenue as it went up in flames, according to CBS Chicago.

Officials reportedly found the body of John Conta Sr. in the home's hallway and his wife Janice Conta in a bedroom on the home's first floor, NBC Chicago reports. Both were in their 60s. The body of 5-year-old Matthew Meier, the couple's grandson, was found in the basement. Police believe all three of them were shot before the blaze was set. An autopsy was set for later Thursday and an investigation is ongoing.

Just the night before the shooting, according to Patch, the family had gotten together in the home to celebrate Matthew's fifth birthday.

"The grandparents adored him, so the mom left the 5-year-old with the grandparents, and unfortunately something tragic happened in that house," Michael Kaufmann, Oak Lawn detectives chief, told ABC Chicago. "I don't know if we'll be able to fully understand why."

John Jr. had stayed in the home with his parents for the past few months, a neighbor told the Chicago Tribune. His parents had lived in the home for more than a decade and Janice was reportedly an active volunteer at St. Linus Roman Catholic Church in Oak Lawn.