Police in Allegheny County, Pa., say five people are dead after unidentified shooters attacked what appeared to be a backyard party in the borough of Wilkinsburg late Wednesday night.

Four people — three women and a man — died at the scene. A female victim died at the hospital. Two men are in critical condition and a woman is in stable condition.

Lt. Andrew Schurman of the county's homicide unit said in a statement, "It would appear from early examination of the scene that a backyard party/cookout was being held at the rear of the home. The ballistic evidence on the scene leads police to believe that two different weapons were discharged from two different people."

Schurman said shots were fired from an alley to the rear of the property, and that "partygoers appeared to try to run into the residence at which point a person on the side or backyard adjacent to the residence fired at the back porch."

"All four of the individuals who died at the scene died on that back porch," Schurman added.

Authorities believe at least two suspects fled on foot.

Neighbors tell the Pittsburgh Post Gazette that they were awakened by gunshots and screaming, around 11 p.m.

Resident Kayla Alexander told WPXI-TV that she was walking home when she heard at least 20 shots and then saw people running from the area.

A motive for the shooting wasn't immediately clear.

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