Matthews was searched and questioned after a school resource officer was alerted to a trespasser inside the school around 9:30 a.m., police said. The employee called administrators and police, who went on the bus to investigate.
Charlotte-Mecklenburg police say Damon Wright had brought a loaded gun in his backpack to Harding High School.
A 15-year-old boy was arrested Tuesday at Clarke Central High School after he was said by police to have been verbally abusive to several staffers.
No one reported anything about a weapon during the school day.
That student was charged with unlawful possession of a weapon and disorderly conduct.
School officials are increasing security on the campus Wednesday. A ninth-grade student was charged with a juvenile citation after that incident and released to his family.
An Annapolis teen faces charges Wednesday after being found in possession of a loaded gun at school.