School resource officers say they made the discovery while towing vehicles in the parking lot that didn't have the correct parking sticker.
The car belongs to Byrd's father. The teen is charged with possession of a weapon on school grounds, a felony offense.
Terri Sessoms, Public Information Officer for Johnston County Schools, said "Disciplinary action will be in line with the JCS Code of Conduct."
Any suspension would be decided after the investigation was complete.