A 15-year-old 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 Washington state home, according to court documents.

The 15-year-old, who is not being named by NBC News 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.

Five people — two adults and three children, 7, 9 and 13 years old — were found dead shortly before 5 a.m. Monday following reports of a shooting 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 Office detective wrote in an affidavit.

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

The 15-year-old was taken into custody on 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 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 detective with the sheriff’s office wrote in a probable cause statement.

Investigators say that claim is false, and that the teen staged the scene to blame one of the victims, Det. 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 the teen 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,” the attorneys said.

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

Attempts to reach family members have been unsuccessful. 

A neighbor told KING-TV that the couple homeschooled their children and said the kids were active in the community and well-known.

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 killed himself, the detective wrote.

King County Councilmember 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. “Mark’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.”