Police in western Pennsylvania are searching for two suspects who ambushed a backyard party near Pittsburgh, killing five people execution-style and wounding three others.
One gunman armed with a 40-calibre handgun shepherded victims from the home's yard on Wednesday evening toward an alley where a second gunman armed with "an AK-47 type" rifle shot them in the head, Allegheny County District Attorney Stephen Zappala Jr said.
"The murders were planned, calculated, brutal," Zappala said on Thursday.
The motive for the fatal shooting of four women and one man in a residential neighbourhood of Wilkinsburg, east of the city, was still unknown, but authorities were exploring whether it might be drug-related, Zappala said.
In addition to the five killed, one of whom was pregnant, three people were wounded.
Two males remain in critical condition.
The people who died ranged in age from 25 to 37, officials said, though family members said the oldest fatality was 38. Three of the five who died were siblings.
One of the dead, Tina Shelton, was a mother of five who held down three jobs and was encouraged by family members to attend the barbecue as a way to relax after work, her father Vernes Pugh and other relatives told local station WPXI-TV.
After gunning down their victims, the suspects fled, police said.
Four died on the back porch next to the alley, while another woman died at a hospital.
The massacre in Wilkinsburg, a borough of about 15,000 mostly lower and middle-income residents, is the latest in a series of mass shootings that have made gun control a matter of heated debate in the United States.
