The parents who called police after discovering their teenage son had ordered bomb-making materials on the Internet likely averted disaster at his high school, a sheriff said Tuesday.

Ryan Schallenberger, 18, was arrested Saturday after his parents called police because he had ordered 10 pounds of ammonium nitrate, which they retrieved after getting a delivery notice from the postal service, authorities said.

"We applaud these parents and we're very thankful they chose to be concerned and they chose to get involved. We feel like they saved a lot of life in our county," Chesterfield County Sheriff Sam Parker said Tuesday on ABC's "Good Morning America."

Schallenberger's parents had sought help from mental health experts even earlier in the week when he slammed his head into a wall, but the clinic offered no help, authorities said Monday. His parents took him to a hospital but he was not badly injured, said prosecutor Jay Hodge.

Schallenberger was charged with making a bomb threat and was to be charged Tuesday with possession of bomb-making material, Hodge said. The prosecutor said he would request at a bail hearing Tuesday that the teen undergo a mental health evaluation.

Schallenberger's mother and stepfather are "heartbroken," Parker said Tuesday.

"They were very concerned about his future education. I kind of explained to them and told them we've got to deal with two options here, we've got to deal with his education or with his life," the sheriff said.

Ammonium nitrate is a fertilizer that can be used as an ingredient in explosives and was employed in the deadly 1995 Oklahoma City bombing. Authorities said Schallenberger bought the ammonium nitrate on eBay.

Police said that after they were called by his parents, they discovered a hate-filled journal lauding the Columbine killers, an audiotape to be played after Schallenberger died during his rampage and a year's worth of plans for the bombing that included a hand-drawn map of the school.

"He's just a soft-spoken little kid," Hodge said. "But he's done something and threatened to do something that's very violent."

Schallenberger was assigned a lawyer, William Spencer, who did not return calls from The Associated Press.

Schallenberger's mother and stepfather, John and Laurie Sittley, could not be reached for comment. Their phone number was unlisted, they did not attend the hearing and their home about 10 miles from the school was blocked by "No Trespassing" signs.

Authorities said Schallenberger's journal did not specify targets of an attack, or a date that he planned to carry it out. Police Chief Randall Lear said Schallenberger was "just mad at the world."

Authorities checked the school for bombs during the weekend, and students walked through newly installed metal detectors and past law officers on Monday.

Acquaintances said they were surprised by the allegations against the straight-A student.

"He wouldn't hurt a flea," neighbor Carl Parker said. "People just don't know him like I do. He's a good kid."

Students said Schallenberger often ate alone in the cafeteria. "I never thought he'd be the dude to do something like this," said James Ford, a 16-year-old sophomore.

Chesterfield is a town of about 1,500 people in northeastern South Carolina near the North Carolina line.