A 16-year-old Garfield High School student was arrested on campus after police say he was found carrying a semi-automatic ghost gun hidden in his pants, triggering a wider investigation that later uncovered suspected firearm manufacturing activity at his home.

San Diego Police said officers took the teen into custody at the school without incident May 6.

Authorities say the teen was armed while on campus, with a handgun tucked into his pants.

Investigators later searched the teen’s residence and reported finding materials and equipment they believe connected to weapons production.

Among the items recovered were a 3-D printer, carbon filament, a handgun magazine, ammunition, and evidence allegedly tied to the creation of multiple weapons, including 3-D printed machine gun conversion devices.

Firearms expert and trainer William Desy described how accessible the technology can be, saying, “If you have a 3-D printer and you have some software, you can pretty much make anything you want to make,” he told NBC 7.

The teen may have gone beyond possession and manufacturing, he is suspected of supplying guns to classmates and is also a suspect in a recent robbery at a local trolley station.

San Diego police spokesperson Ashley Nicholes said the response was immediate once concerns were raised. 

“I know this is concerning to parents, and we want everyone to know when we get reports of anything like this, our team is going to act swiftly,” Nicholes told NBC.

School leadership also moved quickly following the arrest. In an email to parents, Garfield High School Principal Guillermo Medina stated that “bringing a firearm onto school campus results in an automatic recommendation for expulsion, and we will be pursuing that recommendation in this case.”

The teen was booked into a Juvenile Detention Facility on multiple charges, including robbery, illegal gun possession, and gun manufacturing.

“Building a handgun with a 3-D printer is not complicated,” Desy warned.