From the article:
Kitsap County sheriff's Deputy Scott Wilson says the teen was arrested Thursday for investigation of possessing a dangerous weapon on school property. The gun was not loaded.
Wilson says a deputy went to the school after a child told a parent about seeing the gun and the parent called 911. The deputy found the teen at lunch and asked whether he had anything in his backpack. Wilson says the student told the deputy about the semi-automatic handgun.
Wilson says it appears that the boy never threatened anyone although multiple students at John Sedgwick Junior High saw the gun.
Every gun in the hands of a child must first pass through the hands of an adult.