WILKINSBURG, Pa. — Police were seeking to identify suspects in a deadly ambush attack by two men who methodically shot and killed five people, including a pregnant woman, at a backyard cookout.

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 of the shootings.

Police have no suspects and 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 a man were killed as they rushed toward the back porch to seek cover as 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.

The medical examiner officially ruled the death of the fetus a homicide Thursday afternoon, bringing the fatalities in the late Wednesday night ambush attack to six.

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.

Although Wilkinsburg has a reputation for violence, Jones said it’s rare in his neighborhood.