The Virginia Beach jury deliberated on the fate of Philip Bay, 19, for two hours Monday before rejecting the defense's argument Bay was not guilty by reason of insanity, the (Norfolk) Virginian-Pilot reported.
The jury found him guilty of offenses including manufacturing or possessing an explosive device with intent to cause harm, possessing or using a sawed-off shotgun and soliciting or recruiting for an act of terrorism, the newspaper said.
Because Bay was a juvenile aged 17 at the time of the offenses, a judge rather than a jury will determine his sentence.
Bay's defense team did not dispute Bay's intent to kill at least 30 people on April 20, 2009, at the high school he said he hated.
But the defense asked they jury for a verdict of not guilty by reason of insanity based on testimony from mental health experts and numerous journal entries and hours of video Bay made in the past two years.
In a journal entry from September 2007, Bay wrote: "It's like everyone I lay eyes on I want to kill. ... I tell you this will be a massacre for the ages."
That was "the face of insanity, the voice of insanity," defense attorney James Broccoletti argued.
Rejecting the insanity argument, prosecutors said Bay was calculating, manipulative and bent on revenge after spending time in juvenile detention for bringing a hoax explosive device to school in April 2007.
Bay will be sentenced Feb. 23 and will remain in jail until then, the Virginian-Pilot reported.