Allegheny County Lt. Andrew Schurman said that four women and one man were killed in the shooting at a house on Franklin Avenue in Wilkinsburg, just east of downtown Pittsburgh. Schurman said four of the victims were killed on the home's back porch. A fifth victim died from her injuries at a local hospital.
Allegheny County police said two injured men were in critical condition early Thursday, while a woman was in stable condition, Fox News reported.
Schurman described the gathering at the home as "a backyard party or cookout of some sort", but did not elaborate further. He said gunshots came from two distinct locations but police don't believe anyone at the party fired back.
"It looks like right now they were all fleeing toward the back door of the residence when the second gunman fired from the side of the yard," he said. "They all seemed to get caught on the back porch."
Investigators said the shooters appeared to have fled the scene on foot. No one was in custody early Thursday, and the motive for the shooting was not immediately clear.
Neighbors told local media outlets that they heard between 20 and 25 gunshots.
"It went on for almost a minute," James Boyd told the Pittsburgh Post-Gazette. "I thought it was maybe the pipes bursting. But then we realized it was gunshots. We've had trouble in this neighborhood before but never this close to home."
An unidentified woman who said she lived one house away from the shooting scene told the Pittsburgh Tribune-Review that her neighbors had a cookout earlier in the day and were still in their backyard when the shots rang out.
"It sounded like a war," she said.