Police say gunmen deliberately targeted at least one or two of the victims of a mass shooting at a backyard party in suburban Pittsburgh that killed five and wounded three others late Wednesday.

“The murders were planned. They were calculated,” Allegheny County District Attorney Stephen Zappala said.

Four women and a man were killed at the gathering in Wilkinsburg, Pa., while rushing toward a back porch to escape the hail of gunfire. The assailants fired at as many as 15 adults who were playing cards and having a late-night cookout in the yard. The suspects fled on foot.

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

Chanetta Powell was pregnant and was due in May.

Zappala said authorities are not certain about a motive in the shooting, but drugs or retaliation were not ruled out as possibilities.

“We haven’t seen something like this [in Allegheny County] for quite some time,” Zappala said in the Pittsburgh Post-Gazette. “It’s one of the most brutal shootings I’ve seen.”

Carl Morris and his son, Robert, were getting ready to leave their house across the street when they heard a volley of three shots, a pause, then gunfire lasting more than a minute.

Robert Morris said he saw children run onto the small back porch and heard someone scream, “Mommy, Mommy.”

“It was terrible,” the younger Morris said.

The Morrises said Brittany Powell lived at the home with a daughter who was about 6 or 7 years old.. They said the house was considered a “safe haven” in the neighborhood.

Police said they found one pile of shell casings just outside the yard in an alley, where they believe the .40 caliber pistol was fired, Zappala said. They found more shells along a fence that separates the house from a neighbor’s yard, which is where Zappala said a rifle was fired.

Bullet holes were visible Thursday around the porch addition. Tables and chairs, some tipped over, remained in the backyard, signs of a party quickly abandoned.

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, has lived 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 has been rare in his neighborhood, which is about a block off a major street about a half-mile from Interstate 376, the major commuter artery through Pittsburgh’s eastern suburbs.

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

— With AP