A teen whose mom and twin sisters were among five relatives murdered inside their Pennsylvania apartment was spared — because he was away from home at the time, officials said Tuesday.

Joshua Campbell, 17, had been staying with friends in Willingboro, NJ, when his aunt, Shana Decree, and her daughter, Dominique Decree, went on a killing spree at the family’s home in Morrisville, said Morrisville Police Chief George McClay.

At a press conference, Bucks County District Attorney Matthew Weintraub said locating Joshua was “one bit of good news” in the disturbing slayings.

“We have found him alive. He is safe from harm,” Weintraub said.

Among the dead are Joshua’s mother, Jamilla Campbell, 42, his 9-year-old sisters, Imani and Erika Allen, as well as his cousins Naa’Irah Smith, 25, and Damon Decree Jr., 13.

Their bodies were discovered just after 4 p.m. Monday, but it’s unclear when they died.

While in custody, Shana claimed to investigators that the familial carnage was the result of a botched murder-suicide plot. She told cops that “everyone at the apartment, including the children, wanted to die” and that at one point, everyone began “talking about suicide.”

Weintraub was mum on details surrounding the slayings, including a possible motive and exactly how each victim was killed.

“I am sure that you’re going to ask me why this has occurred, what the motivation is, and as confusing as it was last night, we are no closer to understanding that in the harsh light of day,” he said.

Weintraub grew emotional as he publicly identified the victims and had to compose himself when he came across the names of the little girls, Imani and Erika.

“I wish I didn’t have to report it. I wish we didn’t have to deal with it,” he said, shaking his head.