Michele Cossey bought her home-schooled son a .22-caliber handgun, a .22-caliber rifle and a 9 mm semiautomatic rifle, authorities said. The teenager felt bullied and tried to recruit another boy for the possible attack at Plymouth Whitemarsh High School, authorities said.

Acting on a tip from a high school student and his father, police on Wednesday found the rifle, about 30 air-powered guns, swords, knives, a bomb-making book, videos of the 1999 Columbine attack in Colorado and violence-filled notebooks in the boy's bedroom, Montgomery County District Attorney Bruce L. Castor Jr. said.

Cossey, 46, of Plymouth Meeting, bought the rifle, which had a laser scope, at a gun show on Sept. 23 and provided police with a receipt, investigators said in court papers. The teenager said the two .22-caliber weapons were stored at a friend's house.

The teen was ordered Friday to remain in juvenile detention.

His mother was charged with unlawful transfer of a firearm, possession of a firearm by a minor, corruption of a minor, endangering the welfare of a child and two counts of reckless endangerment.

Castor has said he does not believe and attack was imminent or would occur at all. He said Friday that the teen had a "disturbed mind."

"This was a smart kid that clearly believes he was picked on and was a victim," Castor said. "He had psychological issues and began to act out on those feelings."

Police, who searched home with the permission of the teen's parents, also discovered seven explosive devices Castor has described as homemade grenades: plastic containers filled with pellets to which gunpowder could be added. Authorities said one grenade was operable and the others had been in the process of being assembled.

The search did not turn up any ammunition for the most dangerous firearm in the bunch, the assault rifle.

The teen previously attended middle school in the district but had been taught at home for more than a year after voluntarily leaving school, Castor said.