WILKINSBURG, Pa. » Police today sought to identify the two men who ambushed a backyard cookout and methodically shot and killed six people, including a pregnant woman and her fetus.

The gunmen appeared to have targeted one or two of the victims in the Wednesday night attack, and drugs haven’t been ruled out as a motive, said District Attorney Stephen Zappala.

“The murders were planned. They were calculated, brutal,” Zappala said.

Neighbors brought balloons, stuffed animals and prayers to the home today at a growing makeshift memorial. A group from a local church joined hands with neighbors and others to pray in front of the house.

Police were seeking to identify the two men who seemingly worked as a team to shoot and kill the partygoers Wednesday night. Police have no suspects, and officials said today they have no new information to release.

A county executive urged witnesses to come forward.

Allegheny County Executive Rich Fitzgerald said providing any information “can be our first step to stopping the violence in our communities.”

“As a community, we must say enough is enough,” he said.

Four women, one of them eight months pregnant, and one man were killed when a gunman fired a .40-caliber pistol at the partygoers, who were playing cards and having a late-night cookout.

That steered the victims toward the rear porch and door of the house, where an accomplice armed with a 7.62 mm rifle similar to an AK-47 shot them from behind a chain-link fence less than 10 feet from the porch, Zappala said. Two others were critically wounded.

A medical examiner ruled the death of the fetus a homicide, bringing the fatalities in the attack to six.

Community members and religious leaders held a vigil in front of the house Thursday night, praying for the families and calling for an end to such violence.

Wilkinsburg is a poorer, largely blighted suburb just east of Pittsburgh that is known for drug trafficking and gun violence. But neighbors described the street on which the shooting occurred as generally quiet.

Mike Jones, 57, lives in a duplex on a small hill overlooking the alley and backyard where the shooting occurred. He said violence is rare in his neighborhood.

“This is unheard of,” Jones said of the ambush, shaking his head as homicide detectives milled about in the yard and alley. “It doesn’t happen around here.”

The dead included three siblings, Brittany Powell, 27, who lived at the home; Jerry Shelton, 35; and Chanetta Powell, 25, who was eight months pregnant. The other two were Shada Mahone, 26, and Tina Shelton, 37. All had multiple wounds and had been shot in the head.

“My whole family was massacred,” said Jessica Shelton, the mother of the siblings and aunt of the other two killed.