NORRISTOWN, Pa. — The mother of a 14-year-old who authorities say had a cache of guns, knives, and explosive devices in his bedroom for a possible school attack was charged today with buying her son three weapons.

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 a possible attack at Plymouth Whitemarsh High School, authorities said.

“This is not the best parenting I’ve ever seen and she needs to be held accountable,” a Montgomery County district attorney, Bruce Castor Jr., 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, Mr. Castor said.

Ms. Cossey, 46, of Plymouth Meeting, bought the rifle, which had a laser scope, at a gun show on September 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 boy’s father also tried to buy his son a rifle in 2005, but was not allowed to because he was a felon, police said.

The teenager had a brief court appearance today at which the county public defender’s office and prosecutors agreed to continue holding him while they do psychiatric evaluations.

The boy was led out of the courtroom in shackles and he didn’t comment.

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. She was not accused of helping the teenager plot an attack, “but by virtue of her indulgence, she enabled him to get in this position,” Mr. Castor said.