From
CBS News:
A 15-year-old boy who prosecutors said was the mastermind of a failed plot to go on a shooting spree in a suburban school was sentenced Friday to six years in state prison.
...
Authorities said they planned to open fire at Winslow Township High School in Camden County...
...
the teens in the Philadelphia suburb were never able to get a gun. School officials heard about the plans and the boys were arrested before anyone was hurt.
That's my emphasis, BTW. And we have more details
from the (South Jersey) Courier Post Online:
Initially charge[d] with terrorism, the four were arrested after a girlfriend of one reported the plan to school officials.
All four admitted their role in the plan...
...
All four pleaded guilty to conspiring to possess a handgun.