The student is accused of texting photos of the gun to another student at Harmony School and telling him or her not to attend classes.
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Fort Bend County Sheriff's Office said the student was taken into custody after his friend told school officials about the threat.
Deputies said they found the printed 3-D gun inside the child's bedroom after his parents consented to a search of their home.
Investigators learned the student bought plans for $5 to make the 3-D gun, and then superglued the pieces together.
The sheriff's office said the gun was not functional, however, because the trigger and hammer are solid plastic and do not move.
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