NORRISTOWN, Pa. — Tired of being bullied, an awkward, overweight middle-schooler left his peers behind last year in favor of home-schooling.

But if the bullying ceased, Dillon Cossey found no relief from his demons.

Cossey amassed dozens of BB guns, swords, knives and homemade explosives in his parents’ suburban Philadelphia home while quietly planning an attack at the local high school, authorities said.

Perhaps more troubling, they say, his mother provided more firepower in the form of three deadly weapons that she bought for her only child — a small-caliber handgun, a small-caliber rifle and a 9 mm semiautomatic rifle with a laser scope.

“They (the parents) feel sorry for him. They were overindulgent,” Montgomery County District Attorney Bruce L. Castor Jr. said Friday, when both Cossey and his mother Michele appeared in court on related charges.

“I don’t think that they had any idea that he was dangerous,” Castor said. “She’s not any hardened criminal.”

Michele Cossey, 46, grimaced and wept Friday as a judge read the charges against her.

Her son was arrested Wednesday after an acquaintance shared Dillon Cossey’s plan to attack Plymouth Whitemarsh High School with his own parents and then with police.

Police searched Cossey’s bedroom and found the 9 mm rifle and about 30 air-powered guns modeled to look like higher-powered weapons, along with a bomb-making book, videos of the 1999 Columbine attack in Colorado and violence-filled notebooks, Castor said.

Montgomery County District Judge Paul Tressler on Friday ordered the teen held at a youth facility at least until he undergoes psychiatric testing. He also asked for academic progress reports on the teen, who was described by Castor as a “smart kid” with “mental disturbances.”

“I suspect that he was a target for bullies because he was overweight and not fully developed socially,” Castor said. “I also think that his mental illness would have exaggerated the effect of the bullying.”

Dillon Cossey is charged with solicitation to commit terror and other counts.

Michele Cossey, who runs a deli near the county courthouse, declined to comment in court Friday, as did her husband Frank.

A neighbor spoke well of them.

“That family would not hurt anybody, the son included,” said Kathy Joslin, a lifelong friend. “She never would have bought him something thinking that this was something more than just buying him a toy. She made a mistake. She’s human.”