CHESTERFIELD -- One evening last week, Ryan Schallenberger lost his temper.
It started with a disagreement with his mother, said Chesterfield County Sheriff Sam Parker. Then, the 18-year-old, a high-ranking senior at Chesterfield High School, began banging his head against a wall. Deputies were called to the home, off a mile-long, unpaved road.
In the days that followed, Schallenberger's mother and stepfather sought psychological help for him, Parker said. The mother, Laurie Sittley, told the sheriff she had noticed recent changes in her son's personality.
"He was getting a little bit angrier every day, beginning to show some aggression, temper flaring up real quick over small things," Parker said. "It was very unusual for that young man."
Schallenberger was arrested Saturday after Sittley and her husband picked up 20 pounds of a potential explosive Schallenberger had ordered. Later, authorities found other disturbing items.
They included a rage-filled journal that, as far back as a year ago, mentioned a plan to commit an act of violence at the school and a microcassette clearly intended as Schallenberger's post-mortem sendoff to the world.
"I can't get into specifics," said Randall Lear, the police chief in the town of Chesterfield, about 65 miles southeast of Rock Hill, near the rural community where Schallenberger lives. "But he was saying goodbye to the world, and he was wanting people to know why he did what he did, and there was no apology."
Police on Saturday arrested Schallenberger, charging him with making a bomb threat; he's expected to be charged today with possession of bomb-making material. Authorities believe he intended to use the ammonium nitrate as fuel for a bomb he would have detonated at Chesterfield High.
Ammonium nitrate, the material used in the 1995 Oklahoma City bombing, can be used as an explosive when combined with diesel fuel or another accelerant. Lear said Schallenberger's diary contained plans for a "nail bomb" that would spew nails, nuts and bolts and other metal fragments that would ricochet off concrete walls, able to kill and maim dozens.
Schallenberger's diary spoke favorably of the 1999 school shooting in Littleton, Colo., when two students slayed 13 before killing themselves. Authorities said the journal refers to his plot as "Columbine III," after the Colorado killings and, presumably, last year's shooting deaths of 33 at Virginia Tech.
Sunday was the nine-year anniversary of the Columbine killings, and April 16 was the one-year anniversary of the Virginia Tech massacre. But authorities said they don't know whether Schallenberger intended to commemorate the anniversaries with a mass killing of his own.
The diary detailed Schallenberger's dissatisfaction with the world in general, Lear said, including "rich guys being able to get hot girls, the girls trying to use the guys for status people being frivolous."
The first entries in March 2007 reflected his anger and alluded vaguely to violence at the school, said Lear, who read the diary Sunday. As they progressed, so did his plan, which evolved into a step-by-step plot.
"It was very specific -- what to do when, how to carry it out. He had the plan ready to go," Lear said. "He never singled out any group of people, let alone any individual. He just kept acknowledging he was very angry."
On Monday, Schallenberger remained in the Chesterfield County jail after a brief court appearance in which a judge assigned attorney William Spencer to represent him. Spencer did not return calls Monday. The judge is expected to rule today whether to order the 18-year-old to undergo a psychiatric evaluation and whether to set bond.
Monday morning, Chesterfield High students had to walk through two metal detectors officials transferred from the county courthouse to the school. Officials also sent 27 armed officers to the school. The news of Schallenberger's arrest kept most of the student body -- as much as 70 percent of the 544-student enrollment -- at home Monday, said school district spokesman Ken Buck.
Schallenberger is an excellent student ranked third in his class, Lear said. He has no history of bad behavior; he's a member of the school's academic bowl squad and last school year was named a Newberry Scholar by Newberry College, about 30 miles northwest of Columbia. The college's Web site lists him as a prospective student.