Ryan Schallenberger, 18, was arrested Saturday after his parents called police when 10 pounds of ammonium nitrate was delivered to their home in Chesterfield and they discovered the journal, said the town's police chief, Randall Lear.
The teen planned to make several bombs and had all the supplies needed to kill dozens at Chesterfield High School, depending on where the devices were placed and whether they included shrapnel, Lear said. Ammonium nitrate was used in the Oklahoma City bombing in 1995 that killed 168 people.
"The only thing left was delivering the bombs," the police chief said.
Schallenberger kept a journal for more than a year that detailed his plans for a suicide attack and included maps of the school, police said. The writings did not include a specific time for the attack or the intended targets.
He also left an audio tape to be played after he died explaining why he wanted to bomb his school. Lear wouldn't detail what was on the tape except to say Schallenberger was an angry young man.
"He seemed to hate the world. He hated people different from him - the rich boys with good-looking girlfriends," Lear said.
In his writings, Schallenberger said he admired the two teens who killed 13 people at Columbine High School in Colorado in 1999 before committing suicide, Lear said. The attack happened nine years ago Sunday, but Lear said investigators do not know whether there was any link between the anniversary and Schallenberger's plans.
Schallenberger was one of the top students at the high school of about 580 students and had not caused any serious problems before his arrest, principal Scott Radkin said.
The school's Web site lists Schallenberger as a member of the 2007 academic bowl squad. He won an academic award from Newberry College in the last school year.
The teen was in the Chesterfield County jail Sunday night, charged with possessing materials to make bombs, the police chief said. A bond hearing was scheduled for Monday. Other than the bomb-making material, no other weapons were found at his home, Lear said.
Lear said Schallenberger did not have an attorney. His parents could not immediately be located Sunday by The Associated Press.
Security will be tightened at the school when students return Monday. Students will walk through metal detectors borrowed from a courthouse, and bomb and drug sniffing dogs have been called in. Lear said he does not expect any problems.
Chesterfield is a town of about 1,500 people in northeastern South Carolina near the North Carolina line.