15-year-old boy charged in mass slaughter of parents, 3 siblings could get less time in lock up if his case stays in juvenile court

The 15-year-old boy accused of murdering his parents and three siblings in the family’s Washington state mansion could spend less time behind bars if his case doesn’t elevate to adult court, prosecutors said.

The unidentified teen suspect can only be held until he’s 25-years-old — less than 10 years from now — if he’s convicted in juvenile court, according to the King County Prosecuting Attorney’s Office.

Prosecutors on Friday argued the gruesome case should advance to adult court where the teen faces life in prison for allegedly shooting his parents — Mark, 43, and Sarah Humiston, 42 — his two brothers and sister, ages 7, 9 and 13, to death, and injuring his 11-year-old sister, in a bloody massacre on Monday.

Defense attorney Amy Parker described the alleged teen killer as a caring boy, who has no criminal history, and enjoys mountain biking and fishing.

“We want the court to know that multiple people in the community have reached out to us who know our client, and they have attested to his good character,” she said in court on Friday.

“He has been described by them as kind and caring. This is a boy who has many friends, has pro-social interests, and has been a positive contributor to his community.”

Deputies responded to the Lake Alice Road home around 5 a.m. on Monday and found the victims’ lifeless bodies covered in blood and riddled with bullets to the face, head and body inside the family’s $2 million home in Fall City, according to charging documents obtained by the Post.

The teen is accused of hatching a disturbing plot to stage the massacre as a murder-suicide carried out by his 13-year-old brother and be the family’s sole survivor, according to the charging docs.

The report claims the 15-year-old tried to say his brother, who was murdered, committed the murderous rampage after he was caught watching porn the previous evening.

Detectives also allege that the accused teen killer attempted to stage the crime scene to appear as if his brother carried out the heinous act and “placed” a pistol in his hand after he was killed.

The 11-year-old sister of the suspect, the only family member to survive the killing spree, said her brother used her father’s silver handgun to fatally shoot her parents, her brothers, Benjamin and Joshua, and her little sister Katheryn, according to charging documents.

According to the documents, the teen’s murderous rage came after he failed some tests at school and got into “a lot of trouble.”

The young girl was sleeping in her room when she awoke to the deafening sound of gunshots.

She tearfully told investigators that her older brother barged into her bedroom and allegedly opened fire on her, striking her in the hand and neck, and allegedly killed their younger sister, with whom she shared a room.

The girl then “pretended to play dead” as her brother re-entered the room and stood next to her bed before he existed again, according to the charging docs.

She fled the home through her bedroom window when she felt her brother wouldn’t catch her and ran to a neighbor’s house, where she phoned the police.

Deputies responded to the family home, about 30 miles outside Seattle, after receiving 911 calls from the alleged killer and his surviving sister, according to the docs.

The injured girl, who was taken to Harborview Medical Center following the massacre, identified her 15-year-old brother as the shooter.

Deputies immediately took the juvenile into custody after discovering the bodies and his sister IDing him as the suspect, prosecutors said.

The teen was charged with five counts of first-degree aggravated murder and one count of first-degree murder and is detained at the Clark Child and Family Justice Center in Seattle.

A judge is expected to make a decision on what court the teen will be tried during a hearing on Jan. 8, 2025, prosecutors said.