A mother accused along with her teen daughter of killing five family members in a Pennsylvania home Monday told authorities everyone in the home wanted to die, according to a probable cause affidavit. Shana Decree, 45, and 19-year-old Dominique Decree are charged with five counts of criminal homicide and a conspiracy count. The victims were discovered after a caseworker conducting a welfare check found the mother and daughter "disoriented" and five people dead in the Morrisville apartment Monday, the document says.

Bucks County District Attorney Matthew Weintraub identified the victims as Shana Decree's two other children, 25-year-old Naa'Irah Smith and 13-year-old Damon Decree Jr.; Shana Decree's sister, 42-year-old Jamilla Campbell; and Campbell's 9-year-old twin daughters, Imani and Erika Allen.

A visibly shaken Weintraub said Tuesday authorities are still trying to piece together a motive and how the killings were carried out. He said investigators are considering the possibility the slayings were part of an attempted murder-suicide. He said he couldn't speak to the statements allegedly made by Shana Decree as outlined in the affidavit.

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"As confusing as it was last night, we are no closer to understanding that in the harsh light of day," Weintraub said.

Weintraub said a coroner would determine causes of death. Sources tell CBS Philly the victims were strangled.

"I just feel very confident that we have the two killers locked up that committed these atrocious, atrocious murders," Weintraub said.

Shana Decree, left, and Dominique Decree, right CBS Philly

The probable cause affidavit says the caseworker knocked at the door but received no answer Monday afternoon. She asked a maintenance worker to open the apartment, where they found Shana and Dominique Decree in bed — one unconscious and the other suffering from a seizure, according to CBS Philly — and the apartment in disarray. Morrisville police responded and found two adults and three children dead in another bedroom.

The probable cause affidavit says Shana and Dominique Decree were transported to the hospital, where Shana Decree told police "everyone at the apartment, including the nine-year-olds and the thirteen-year-old, wanted to die."

"Shana advised that all, including the children, were talking about suicide," the affidavit read.

Both mother and daughter at first denied knowing what happened and blamed the killings on Campbell's boyfriend and two other men, according to the affidavit. Dominique Decree had "visible injuries to her neck," asked if her family was alive and "repeatedly advised her wish to die."

The document says Shana Decree eventually told investigators that she killed one of the victims, she and Dominique killed another victim and that Campbell killed two victims before Campbell was killed by Dominique.

Weintraub said eight family members lived in the apartment, which he described as "tiny." The eighth family member, Campbell's 17-year-old son, was found safe after a search. Police said he was located in Willingboro, New Jersey, where he was staying with friends, and stressed he was not a suspect, according to the Associated Press.

Morrisville Police Chief George McClay on Monday dismissed Shana Decree's claim that the victims wanted to die.

"When you have two 9-year-olds involved, two 9-year-olds can't make that decision, and a 13-year-old. Is it something in the adults' minds? I don't know, but it's surely not in 9-year-old minds," McClay said. "It's a sad day for us. As much as I've seen over my career, this is the saddest case I've ever had."

Shana Decree is being held without bail and Dominique Decree was expected to be arraigned later Tuesday, Weintraub said. It wasn't clear whether the women had lawyers.