Teen, 15, charged with murder in mass slaughter of his parents, 3 young siblings in swanky Seattle suburb

A 15-year-old boy was charged with murder three days after he allegedly shot his parents and three young siblings to death in a bloody scene inside their lavish Washington state mansion. 

Prosecutors charged the teenage gunman — who was not identified due to his age — on Thursday with five counts of first-degree aggravated murder and one count of first-degree attempted murder, according to the King County Prosecuting Attorney’s Office.

They said the teen “systematically murdered” his father, mother, two brothers and sister and attempted to murder his other sister — and then staged the bloody scene before first responders arrived in an attempt to pin the killings on his dead 13-year-old brother, who was shot several times in the head, according to the charging documents. 

He faces life in prison if he is charged as an adult, prosecutors said. 

The bodies of Mark and Sarah Humiston and three of their children — ages 6, 9 and 13 — were found riddled with bullets to the face, head and body inside the family’s $2 million home in Fall City, a suburb of Seattle, around 5 a.m. on Monday.

A sixth victim, an 11-year-old girl, was shot twice and survived the horrific massacre, according to the charging documents.

Deputies responded to the Lake Alice Road home — a stunning waterfront property — after receiving a 911 call from the alleged murderous teen, who claimed his younger brother killed his family and then committed suicide out of fear of being caught viewing pornography. 

At the same time, police received an emergency call from a neighbor who reported the 11-year-old survivor was shot and bleeding from the neck and hand — and identified her 15-year-old brother as the shooter. 

Deputies then found the lifeless bodies of the parents and child victims inside the house, prosecutors said, and immediately took the juvenile into custody. 

The alleged killer’s sister managed to escape the home during the slaughter and was eventually taken to Harborview Medical Center in Seattle after receiving medical attention from a neighbor.

The lone survivor was released from the hospital on Wednesday, a hospital spokesperson confirmed to USA Today.

The King County Medical Examiner ruled each death a homicide, according to the charging docs. 

Defense attorney Amy Parker on Tuesday described the teen, who has no criminal history, as a young boy who “enjoys mountain biking and fishing.” 

The devastated community of about 2,000 — shaken by the shocking quintuple homicide — held a candlelit vigil for the slain family some described as looking “perfect” from the outside.

“It hits me really hard,” said Pastor Carrie Bland, who organized a candlelight vigil at Fall City Methodist Church on Tuesday night, KOMO News reported. 

“I think about not just the loss of children but the parents and the impact that that has, it’s a ripple effect through the community ’cause every person touches multiple people.”

Humiston, 43, was a longtime electrical engineer at Hargis Engineers in Seattle, and his wife, 42, was reportedly a registered nurse, though it’s unclear whether she was still practicing.

The 15-year-old is being held in secure detention at the Clark Child and Family Justice Center in Seattle.

He is due back in court on Friday.