A 16-YEAR-OLD girl and her boyfriend are accused of murdering her grandparents before throwing a drug-fuelled house party at their home as their bodies decomposed upstairs.

Cassandra “Cassie” Bjorge, 16, and her boyfriend Johnny Rider, 19, are accused of beating 63-year-old Wendy and Randall Bjorge with a hammer and a baseball bat before slitting their throats in Lawrenceville, Georgia, reports The Sun.

Cops said in court the teens smoked cannabis and invited friends over, sealing two doors to stop the smell of their rotting bodies seeping out, reports WSB-TV.

The pair allegedly spent days at the couple’s home with their decaying bodies, but went on the run after attacking Bjorge’s sister and her boyfriend.

Cops say they planned to murder more family members, including Bjorge’s mum.

Police said Bjorge has confessed to the killings but her boyfriend hasn’t said a word.

Detective Dave Brucz said: “She admitted after the murder she was texting family members because they were worried about (the grandparents), and she was pretending to be Wendy.”

Gwinnett County Police discovered the bodies on April 8 after being called to reports of an assault at the house.

Bjorge’s sister called police after claiming the pair attacked her and her boyfriend with a baseball bat.

The pair fled the scene but were arrested later.

Police claim the couple used a tire iron, hammer and baseball bat to beat Wendy and Randall, before slitting their throats with butcher’s knives.

Det Brucz told court: “Johnny began to attack the grandmother.

“Bjorge then said she had a surge of energy.

“She then dragged her grandmother into her grandfather’s bedroom. She was duct taped.”

Authorities claim Bjorge and Rider decided to murder the grandparents because they “basically had enough” of them.

They also allege that the pair planned to murder Bjorge’s mum Amanda Sterling and several members of Rider’s family.

This article originally appeared on The Sun.