Walton County deputies said they were called to the boy's home after his mother found a knife sewn into the lining of his jacket, The Atlanta Journal-Constitution reported Wednesday.
In a search of the boy's room Monday, investigators found what appeared to be a pipe bomb and a hand-made hand grenade the teenager had allegedly made.
The boy, whose named was not released, was arrested and held at a youth detention center.
Police said they had not determined what the teen planned to do with the devices.
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