A man fatally shot his girlfriend, her daughter and their 1-year-old child before turning the gun on himself, and authorities said what lay behind the shooting was still being investigated.
The shootings happened late Sunday night in a home rented by the family.
Police believe that Barry Hardesty, 43, shot his 38-year-old girlfriend, Lynette Gasparre, and then her 7-year-old daughter, Quinn Gasparre, and the couple's 1-year-old daughter, Nina Gasparre-Hardesty. He then turned the gun, a .357-caliber handgun, on himself.
"There is no indication of what caused this tragedy at this point," Shaler Township Police Chief Jeff Gally told the Pittsburgh Tribune-Review.
Neighbors told the newspaper that they heard sounds of a loud argument, followed by gunshots about 15 to 20 minutes later.
Quinn's body was found in a hallway and the bodies of her mother, Lynette and Nina were found on a bed. Hardesty's body was found on the bedroom floor. Police said he may have still been breathing when authorities arrived but soon died.
Investigators recovered the handgun from the house, the Pittsburgh Post-Gazette reported.
Police described the neighborhood as quiet and largely crime-free. The home where the shooting occurred is one of about 10 houses on a dead-end street. The family appeared to have moved in in the last three or four weeks, Gally said.
On Monday, crime scene tape was wrapped around the property of the split-level home, which had a Chevy Silverado pickup truck and Dodge Challenger sitting in the driveway. Outside, several people stood and watched investigators move in and out of the house.
The Allegheny County Medical Examiner's office released the names of those killed and ruled that Hardesty committed suicide. Gasparre, Quinn and Nina's deaths were ruled homicides.
Shaler Township is a residential community of nearly 30,000 just minutes from downtown Pittsburgh. Gov. Tom Corbett lives in a farmhouse in Shaler, but a spokesman said Monday the shooting was not near his home.
Corbett was in Shaler last week as he recuperated from back surgery, and had returned to Harrisburg by Saturday, his spokesman said.