The mother and daughter charged with killing five of their relatives in suburban Philadelphia admitted to cops that they planned a murder-suicide because “everyone … wanted to die,” according to new court papers.

The disturbing scene unfolded inside a two-bedroom apartment in Morrisville, Pa. — where a caseworker from the Bucks County Children and Youth Department found victims Naa’Irah Smith, 25, Damon Decree Jr., 13, Jamilla Campbell, 45, and 9-year-old twins Imani and Erika Allen slain in one of the bedrooms.

Shana Decree and her daughter Dominique Decree survived — and have since been charged with all five of their murders and conspiracy.

Shana allegedly told investigators that “everyone at the apartment, including the nine-year-olds and the thirteen-year-old, wanted to die,” according to a probable cause affidavit released Tuesday by the Bucks County District Attorney’s Office.

She also said, “all, including the children, were talking about suicide.”

At first, the mother and daughter — who were rushed to Jefferson Bucks Hospital — denied knowing what happened, the affidavit said.

In the hospital, Shana, 45, initially claimed that Campbell’s boyfriend and two unknown men killed everyone — except for her and Dominique. But she later walked back that claim and confessed to killing one of the children. She said she and Dominique also killed a second child.

The twisted pair also blamed one of the deaths on Campbell — with Shana accusing her slain sister of killing Smith.

Dominique, 19, then killed Campbell, Shana told police.

Dominique allegedly admitted to strangling Campbell and said she and her mother murdered two of the children and Smith. Dominique also claimed that Campbell choked one of the kids to death, though it’s not clear which one.

In the hospital, the teen had “visible injuries to her neck” and told cops they were caused by an unknown black male. She also “asked if her family was alive” and “repeatedly advised her wish to die,” the affidavit said.

The bodies were found around 4 p.m. Monday by the caseworker who was conducting a wellness check at the home and had asked a maintenance worker to check the apartment when no one answered.

Inside the first-floor apartment, there was furniture turned over and “broken glass and clutter throughout” and Shana and Dominique were found in bed, appearing “disoriented,” in the same bedroom as the bodies, the affidavit said.

Four of the victims were found on the floor, while Damon’s body was lying in bed.

The caseworker said the apartment wasn’t ransacked when she last visited on Feb. 5. She said eight people, including “multiple children,” were known to have lived in the apartment.

Among those slain were Shana’s two kids, Smith and Damon, and Campbell’s twin daughters, Imani and Erika.

Dominique told investigators that she lived at the apartment with her mother, aunt, brother, sister and two twin cousins.

Shana was held without bail following her arraignment Tuesday morning. Dominique is awaiting arraignment.