Pittsburgh-area Shooting That Killed 6, Including Pregnant Woman, Was ‘Planned’ and ‘Calculated’

— -- The two shooters believed to have been responsible for a deadly shooting at a suburban Pittsburgh home are still at large as investigators try to determine what led to the killings of five adults and one unborn child, including a pregnant woman.

That death toll is likely to rise, Allegheny County District Attorney Stephen Zappala said.

"We're not optimistic about one of the people [who is] hospitalized right now, so we probably lost seven people," he said after touring the scene of the shooting.

The Allegheny County Medical Examiner has released the names of the five adult victims, three of whom – Brittany Powell, Chanetta Powell and Jerry Shelton – were siblings. The other victims were identified as their cousins Tina Shelton and Shada Mahone.

Chanetta Powell's mother Jessica Shelton said her daughter was pregnant and due in May. Later this afternoon, it was ruled that her unborn child's death is being ruled a homicide.

Allegheny County Police said a total of eight people were shot at a home in Wilkinsburg, Pennsylvania Wednesday night. Three females and one male died at the scene and an additional four partygoers were transported to local hospitals. One woman died from her wounds at the hospital. Two males who were transported to the hospital are in critical condition, and one female is in stable condition.

"The murders were planned. They were calculated," Zappala said.

Zappala added the shooters weren't "just squeezing off shots."

"They were all head shots," he said.

The deadly shooting reportedly happened when two unidentified men arrived at the backyard of a home at around 10:54 p.m. Wednesday. There was a group of people were "playing cards and cooking out," according to police.

"They basically herded people to a position in the yard," Zappala told ABC affiliate WATE, saying that one of the shooters had an AK-47 style gun.

Lt. Andrew Shurman of the Allegheny County Police told reporters that based on “ballistic evidence,” police do not believe anyone at the party fired back in return.

The local FBI confirmed it is supporting the police and sheriff’s department in the investigation.

Zappala said investigators have been able to rule out some possible motives.

"Drugs, retaliation -- there are a number of things we can't eliminate right now," Zappala said.