Doug Stanglin and Carolyn McAtee Cerbin

USA TODAY

The ambush-style killing of five people, including a woman who was eight months pregnant, at a backyard party in a Pittsburgh suburb was a "calculated, brutal" operation, the Allegheny district attorney said Thursday, according to local media reports.

The medical examiner ruled the death of the pregnant woman's fetus a homicide Thursday afternoon, raising the toll to six. Three others were injured when two gunmen opened fire late Wednesday on more than a dozen people attending a party or cookout at a home in the working-class community of Wilkinsburg.

Lt. Andrew Schurman of the Allegheny County homicide unit said four people were found dead at the scene and the fifth died at a local hospital. Two men were in critical condition and a woman was stable, according to police.

Allegheny County executive Rich Fitzgerald said Thursday that the Wilkinsburg community is "filled with grief, shock and anger this morning. We share their grief and offer them our support in the days and weeks to come."

Police said the gunmen barged into the party and began firing.

"The murders were planned, calculated, brutal," Allegheny County District Attorney Stephen Zappala told Pittsburgh's WPXI-TV. He said there were 15 people in the backyard when a shooter armed with a .40-caliber handgun approached from the alley and began shooting.

Zappala told the Pittsburgh Post-Gazette that police believe there were one or two intended targets, and that a relative of the victims might have been one.

“I heard about 30 gunshots, it was just a constant,” Jackie Johnson-Pendleton, a neighbor, told KDKA. “When I came out, people were screaming and running and bodies were lying on the front porch. People’s lives taken like that at the drop of a hat, it’s just insane and it needs to stop.”

Schurman said said the shots were fired from two locations but police don’t believe anyone at the party fired back.

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

As ambulances and police cars converged on the scene, neighbors gathered on the street, some of them sobbing and saying they lost family members, the Associated Press reported.

The victims were identified as siblings Jerry Shelton, 35, Brittany Powell, 27, and Chanetta Powell, 25; and Tina Shelton, 37, and Shada Mahone, 26, according to the Allegheny County medical examiner’s office.

Kayla Alexander, a local resident, told WPXI-TV she was walking home when she heard two dozen shots and saw people running from the area. She said authorities weren't allowing her to get to her home on Franklin Avenue, a usually quiet street lined by two-story brick houses built in the early 1900s.

James Boyd, 70, has lived in a home three doors away from the shooting for 24 years. He told the Pittsburgh Post-Gazette that the gunfire “went on for almost a minute.”

“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,” Boyd said. “I’ve never seen anything like this before.”

In 2001, the Allegheny County community of 15,800 people, was the scene of another fatal rampage when a gunman went on a lunchtime shooting spree at two fast-food restaurants, killing two people and wounding three, according to The New York Times. Ron Taylor, the 39-year-old gunman who left a suicide note, surrendered after a standoff and was later convicted. He is currently on death row in Pennsylvania.