University Park Police Chief Gary Adams says some threats were made in handwritten notes left at Highland Park High School, starting in January. Many others were made by email through sophisticated software designed to mask the source. On one occasion, a handful of .22-caliber bullets were left in a boy's bathroom.
The first of those threats earlier this year disrupted classes at the school in University Park and prompted tighter security measures there.
The suspect's identity was being withheld because of his age, but he's been charged with 17 counts of making terroristic threats.
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