A 15-year-old boy accused of killing his parents and three siblings shot them and then called police to claim that one of the victims killed his family and then himself at their home in Washington state, according to court documents.

The boy, whom NBC News is not naming because of his age, was charged Thursday with five counts of murder and one count of attempted murder in the slayings Monday morning in Fall City.

Two adults and three children — 7, 9 and 13 years old — were found dead shortly before 5 a.m. Monday after a shooting was reported at a home in the Lake Alice Road neighborhood in Fall City, about 25 miles east of Seattle.

An 11-year-old sister who was shot but survived by playing dead managed to escape the home through a window and went to a neighbor’s home, a King County sheriff’s detective wrote in an affidavit.

She was hospitalized and has been discharged, a spokesperson for Harborview Medical Center in Seattle said Thursday.

The 15-year-old boy was arrested the day of the shooting and was being held in a detention facility for juveniles Thursday.

All six criminal counts have been filed with a designation that they are acts of domestic violence, the prosecuting attorney's office said. The attempted murder count has a firearms enhancement, which allows for a greater sentence if the boy is convicted.

About 4:55 a.m. Monday, the 15-year-old called the King County Sheriff's Office and claimed that the 13-year-old who was killed "just shot my whole family and committed suicide, too," a sheriff's detective wrote in a probable cause statement.

Investigators say that the claim is false and that the teen staged the scene to blame one of the victims, Detective Aaron Thompson wrote in the document.

The surviving 11-year-old sibling told police that her 15-year-old brother shot her and her family with a Glock handgun that belonged to their father, the probable cause statement says.

She told investigators that the teenager shot her and then left the room and that she heard someone shouting "stop" and "help" before she escaped, the detective wrote.

Amy Parker and Molly Campera, who are representing the 15-year-old, said Tuesday at his first court appearance that the “law presumes our client is innocent of these charges.” They called him “a 15-year-old boy who enjoys mountain biking and fishing and has no criminal history.”

“I would remind everyone that these are not proven facts, merely allegations, and the law presumes our client is innocent of these charges,” they said.

During Tuesday’s court appearance, the teen waived his right to appear and was ordered to have no contact with the surviving sibling.

Family members could not immediately be reached for comment.

A neighbor told NBC affiliate KING of Seattle that the couple home-schooled their children and that the kids were well-known and active in the community.

The family’s father was shot four times, and the mother had two gunshot wounds, according to the probable cause statement. The three children were also shot.

The evidence appeared to show that the suspect "systematically murdered his mother, father, two brothers, and sister, and attempted to murder his other sister," Thompson, the sheriff's detective, wrote in the probable cause statement.

The suspect "then staged the scene prior to the arrival of first responders" to make it appear that the 13-year-old victim committed the murders and died by suicide, the detective wrote.

King County Council member Sarah Perry called the shooting “a terrible situation.”

“My heart aches for the lives lost and all who are struggling to make sense of this loss right now,” she said on Facebook this week.

The teen's father worked as an electrical engineer for Hargis Engineers, the company said.

“We are blindsided and saddened by the tragic events that have led to the loss of a respected colleague, mentor and friend, as well as the loss of immediate family members,” the company said in a statement. The man’s “leadership and vision were integral within our firm, and he will be greatly missed. Our thoughts are with his surviving family, friends, and colleagues during this difficult time.”