An 11-year-old girl is believed to be the only survivor of a mass massacre perpetrated by a suspected killer in an upscale Seattle suburb.

An 11-year-old girl is believed to be the only survivor of Monday’s massacre at a palatial Washington state home, where five family members, including three young children, were found shot to death, according to local reports.

A 15-year-old boy is behind bars after police found the bullet-riddled bodies of two adults and three young teenagers around 5 a.m. in the family’s $2 million cabin in Fall City, while a sixth victim, the young girl, was shot twice. during the disturbing massacre.

Prosecutors asked the court Tuesday to charge the teen — who has not been identified — with five counts of first-degree murder and one count of attempted first-degree murder, according to the prosecutor’s office of King County.

Judge Joe Campagna ordered the alleged killer to remain in secure juvenile detention while awaiting formal charges, calling the allegations “of the gravest possible severity,” The Seattle Times reported.

Campagna also banned contact with the only member of his immediate family who survived the attack, the 11-year-old girl, the outlet reported.

The teen, who waived his right to attend his first appearance in King County Superior Court, was described by defense attorney Amy Parker as a young boy who “likes to ride mountain bikes and fish.”

She also insisted her client had no criminal history.

Authorities have not released the identities or ages of the victims, although the child victims are believed to be teenagers, with the oldest being around 15, neighbors told FOX13.

Deputies went to the Lake Alice Road home — a beautiful waterfront property — just before 5 a.m. Monday after receiving several 911 calls regarding a “disturbance with gunfire” and discovered that all five members of the family were shot, King County Sheriff’s Office spokesman Mike Mellis said.

At least some of the 911 calls that alerted officers to the shooting came from victims who were inside the home and hiding in the bathroom, KIRO 7 reported.

Officers immediately arrested the teen inside the home, Mellis said, and the young survivor was taken to Harborview Medical Center in Seattle after receiving medical help from a neighbor following the shooting.

As of Tuesday, the King County medical examiner’s office had not released the identities of the slain victims.

Prosecutors are expected to file formal charges Thursday, with an arraignment to follow Friday.