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"Basically without the parents, Chesterfield County would have suffered," said Chesterfield County Sheriff Sam Parker.
"I don't know honestly until I was faced with it, if I could have made the same decision they made," said Chesterfield Police Chief Randall Lear.
Investigators searched Schallenberger's home, confiscating a journal with notes outlining an attack on Chesterfield High School.
They also found enough bomb-making material to kill dozens of his fellow students.
"There is enough ingredients to where it would be a matter of just minutes," said Chief Lear.
Local authorities also swept the high school twice with bomb-sniffing dogs. They found no weapons.
The most damning evidence may come from Schallenberger himself.
"Right now he is very cooperative and he is very confused. We are also looking at the issue of his condition right now to see that we get him help so he can cooperate," said Sheriff Parker.
The principal of Chesterfield High School says Schallenberger had not caused any serious problems before his arrest.
Schallenberger will undergo a mental evaluation when the teen appears in court Tuesday for a bail hearing.