The Olympian reports that police found three guns and ammunition in the boy's home, and arrested him Monday.
Thurston County Deputy Prosecutor Wayne Graham said Tuesday in court that the boy had expressed a "fascination with Columbine," the 1999 school shooting in which two student gunmen killed 12 students and a teacher before killing themselves.
Tumwater police Detective Jen Kolb says police went to the student's home after hearing of the threats to shoot students at Black Hills High School.
A juvenile court commissioner ordered the boy held pending a mental evaluation. Graham says the teen was arrested for investigation of harassment and unlawful possession of a firearm.
Graham says the guns included a 9 mm pistol, a shotgun and an "assault-style weapon."
The boy's mother told the court her son "had some depression issues."