Patrick Bryan Mitchell, 18, was arrested last Friday when officials at South River High School in Edgewater, Md. discovered an unloaded shotgun in the back seat of his car.
Mitchell claims he forgot about the gun, which was from a hunting trip the night before.
South River High School students came to school on Monday wearing camouflage and orange T-shirts which said “#FreeBryan,” reports the Capital Gazette.
Some students hung posters to show their support, but school staff removed them.
According to WUSA 9, the gun was discovered when a school administrator was checking cars for permits and noticed a shotgun shell and part of a gun underneath some clothes in the back seat of Mitchell's car.
The cops were called and Mitchell was arrested after police officers found an unloaded 12-gauge shotgun and shells in his car.
Police also found two Vyvanse pills, which is used to treat ADHD, for which Mitchell did not have a prescription.
The teen was charged with possession of a dangerous weapon on school property and possession of a controlled substance, notes The Baltimore Sun.
Even though school authorities found there was no ill intent, Mitchell may still face expulsion for the gun.