A 15-year-old boy is facing several murder charges for allegedly slaughtering five family members — including three young kids — inside their sprawling $2 million Washington state cabin, Monday, according to cops and prosecutors. 

Prosecutors asked the court on Tuesday to charge the teen — who was not identified — with five counts of first-degree murder and one count of first-degree attempted murder, according to the King County Prosecuting Attorney’s Office. 

Two adults and three young teens were found shot to death inside the tony home in Fall City — a suburb of Seattle — around 5 a.m. Monday, King County Sheriff’s Office spokesperson Mike Mellis said.

Deputies responded to the Lake Alice Road home — a stunning waterfront property — just before 5 a.m. on Monday after receiving multiple 911 calls of a “disturbance with gunfire” and found the lifeless bodies, Mellis said. 

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

“They shot the other family members, I believe there is five total, not including the RP (reporting party) who’s hiding in the bathroom,” one dispatcher said during a call, according to FOX13.

The deputies on the scene immediately arrested a “high-school-age” teenage boy inside the house, Mellis explained.

“It does appear to be a family incident, a domestic violence incident that involves a young man who’s in significant trouble, and involves firearms,” Mellis said of the situation.

“Once bodies were discovered, clearly we understand that this is a hugely significant crime scene,” Mellis explained.

A suburb of Seattle, Fall City has a median home listing of $1.5 million.

Mellis described the city of about 2,000 as a “pretty nice area, low crime rate in general.”

Sheriff Patricia Cole-Kendall told KING-TV that she was “very sad, very disturbed” by the killings.

The shooting involved a family of seven people, King County Councilmember Sarah Perry said in a statement Monday night.

As of Tuesday morning, the names of the victims still had not been released.

One horrified neighbor said a couple and their five children lived in the home, which is now a crime scene.

“I’m just in total shock,” neighbor Lynne Trowern told KING-TV. 

“I keep bursting into tears. That is why I have to go to my daughter’s house because I can’t be here on my own. I just keep seeing the faces of the children.”

The eldest child was around 15, neighbors told FOX13.

The parents supposedly kept to themselves, but the children were friendly and were known to help neighbors out with home projects, they added.

“So polite. Home schooled. It’s unfathomable what’s happened,” a former neighbor, Cameron, remembered of the kids.

“I only saw the children in the driveway yesterday afternoon,” said Trowern. 

“It was very quiet there yesterday up until 4. I think they just came home from somewhere and the kids were running up and down the driveway as usual, one of the boys was playing piano in the garage, and it stared to rain, so I came in,” she recalled.

The children even visited Trowern’s home for the Fourth of July over the summer, she told the outlet.

“The kids would come over on the Fourth of July and play sparklers and everything,” she said. 

The nearby Snoqualmie Valley School District confirmed that at least two of the victims were still “school-age,” though none of them attended the district schools.

With Post wires