Washington state teen accused of killing his family faces adult court

Nearly two years after a 15-year-old boy was arrested in connection with the fatal shooting of his parents and three younger siblings near Fall City, a hearing to determine whether the teenager will be tried as an adult began on Tuesday.

State prosecutors argued the boy, now 17, systematically executed his parents and younger siblings with his father's gun at their home in October 2024. He is charged with five counts of first-degree aggravated murder and one count of attempted murder.

Attorneys representing the teen described a fanatically religious and abusive family dynamic, and they argued the boy developed mental health issues as a result.

The Seattle Times typically does not name juvenile suspects unless they are charged as adults, and a court order has mandated the teen not be named publicly.

Tuesday marked the beginning of a dayslong discretionary decline hearing," in which prosecutors and defense attorneys provide evidence for a judge to rule on whether the teen's case will be transferred to adult court.

Had the boy been a year older, he would have automatically been charged as an adult.

The judge must weigh eight Kent factors, set out by a 1966 U.S. Supreme Court case, including the seriousness of the offense; the sophistication and maturity of the juvenile; the prospects for adequate protection of the public; and the likelihood of rehabilitation.

If the teen’s case is adjudicated in juvenile court, he would be released when he's 25 years old. If he is convicted in adult court, aggravated first-degree murder carries a sentence of 25 years to life for juveniles.

Those killed in the mass shooting were 43-year-old Mark Humiston, 42-year-old Sarah Humiston, and three of their children: Katheryn Humiston, 7; Joshua Humiston, 9; and Benjamin Humiston, 13. The middle child, a then 11-year-old girl, was shot but escaped through her bedroom window to the neighbors' house. She later told investigators the eldest brother shot her.

Jamie Kvistad, a King County senior deputy prosecuting attorney, walked Judge Veronica Galván through the alleged crimes during opening statements. Kvistad described the rural family home as sheltered by trees and adorned with decorations from the youngest girl's birthday celebration 11 days prior.

Sometime before 5 a.m. on Oct. 21, 2024, the 15-year-old entered a code into the lockbox where his father's handgun and a loaded magazine were stored, Kvistad said. She described a cunning killer who shot his father while he was getting ready for work, his siblings while they were still in their pajamas, and his mother while she cowered behind a toilet in her bathroom.

"Bodies, blood, decisions — what to do?" Kvistad said.

She argued the teen shot the 13-year-old, placed the gun in his hand to make it look like a self-inflicted wound, changed his clothes and called 911, affecting a frightened voice to the operator.

Benjamin, the 13-year-old, was found with a gunshot wound to the head and with the Glock in his left hand on his chest. The King County medical examiner’s office determined that he was shot in the head from over 2 feet away, and had another wound from a gun that was fired between 6 and 24 inches away, charges say.

The neighbors, upon the 11-year-old girl's arrival, called 911 seven minutes after the teen made his call. When law enforcement showed up, the teen told them his 13-year-old brother shot the family.

Prosecutors argued that under sentencing guidelines, the teen could be released to a community facility — group homes run by the Department of Children, Youth and Families — after serving 10% of his sentence.

Juvenile rehabilitation administrators with DCYF testified on Tuesday afternoon that youth who were convicted of murder can be eligible to move to a community facility — which is considered confinement but not a secure facility — if the transfer is reviewed and approved by the department.

The seriousness of the alleged offenses, Kvistad said, mandate declining the case.

"(The teen's) actions were lethal, controlled and targeted," Kvistad said.

The teen's attorney, Amy Parker, argued it is highly unlikely DCYF would move him to a group home before his sentence is over.

Parker argued prosecutors were relying primarily on the seriousness of the offense and not on other factors, like the maturity of the boy or his chances at rehabilitation.

The judge can give greater weight to some of the Kent factors than others, and a single factor may be sufficient to provide a basis for her decision.

Parker said during her opening statement that harmful dynamics were at play in the home, which she described as a "religiously insular and sheltered environment."

She said neighbors who were interviewed described worrying that the kids were hoarding food, and Parker claimed the parents sometimes forced the children to miss meals as punishment. One neighbor, Parker said, claimed that the kids were told they couldn't be on the neighbors' property after the Humiston parents learned they were a same-sex couple.

The children stopped being taken to the doctor after the COVID pandemic began, Parker said, and the teen had head injuries that went untreated. The family peddled conspiracy theories, and the children were taught the government and social systems would collapse, she argued.

Parker also said the parents had several guns, including an AR-15 rifle, that were stored unsecured.

"Firearm access is the single decisive factor that turns general youth conflict or emotional distress into fatal multicasualty events," Parker said.

The teen's attorneys will call forensic and psychiatric experts who will speak about his chances at rehabilitation and mental health issues, including psychotic thoughts and bipolar disorder.

Kvistad, the prosecutor, argued diagnoses alone don't establish that the teen would be amenable to rehabilitation.

According to Parker, the teen was described by community members as a loving and responsible child, demonstrating a likelihood of rehabilitation. Relying on the Kent factors, she argued, the case should remain in juvenile court.

Parker said family members and friends described the killings in east King County on that autumn day as "completely out of the blue."

In the Humiston family, she said, "perfection was the standard."

"He wasn't allowed expression with his hair," Parker said. "He had two options: short or shorter.

On Tuesday, flanked by attorneys to his left and TV cameras to his right, the teen's brown hair extended just past his shoulders.

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