Three others were taken from the scene in ambulances. Of those victims, two men were listed in critical condition and a woman was listed in stable condition, police said.
According to authorities, the shooting happened during a backyard party/cookout.
Police said the ballistic evidence on the scene leads investigators to believe that two different weapons were discharged from two different people. Shots were fired from an alley to the rear of the home.
Police said partygoers appeared to try to run into the home, at which point a person on the side or backyard adjacent to the house fired at the back porch.
Lt. Andrew Schurman of the Allegheny County homicide unit said the gunmen barged into the party and opened fire in an ambush-style attack.
Schurman said at least two gunmen were involved, but no one was in custody. A motive wasn't immediately known.
Allegheny County police said at least two gunmen were involved, but no one was in custody.
A witness told Channel 11 News that she was walking home when she heard 26 shots and then saw people running from the area. She said authorities were keeping her from getting to her home on Franklin Avenue, which she described as a quiet street.
Groups of residents were gathered on the street, some of them sobbing and saying they lost family members.
Anyone who saw or heard anything is asked to contact the Allegheny County Police Homicide unit at 412-473-1300. Callers can remain anonymous.
Stay with WPXI.com for updates on this developing story.