A 15-year-old boy accused of killing his parents and three siblings in their luxurious Washington home last October was raised in extreme isolation under a “rigid, militant survivalist ideology,” according to new court documents filed by his defense team.

The teen, whose name has not been publicly released, allegedly shot and killed his parents, Mark and Sarah Humiston, and siblings Benjamin (13), Joshua (9), and Katheryn (7) around 5 a.m. in their $2 million lakeside mansion. His 11-year-old sister survived by playing dead and escaping through a window.

Court filings paint a disturbing picture of the family’s life. The children were homeschooled, cut off from the outside world, and taught to distrust the government and medical professionals. Firearms were reportedly accessible to all family members—including the handgun used in the killings.

Witnesses, neighbors, and extended family described the home as abusive and controlled by religious extremism. The boy’s maternal grandmother even claimed Sarah Humiston was “demeaning and abusive,” and said she had previously threatened to report them.

Prosecutors say the teen staged the crime scene to blame his 13-year-old brother, even placing a gun in the boy’s hand. He called 911 and falsely claimed his brother had killed the family before taking his own life.

Despite the horrific nature of the crime, some who knew the teen described him as respectful and devoted to his family. He now faces five counts of aggravated first-degree murder and one count of attempted murder.