Police say a 16-year-old Garfield High School student was arrested after officers found a semi-automatic ghost gun and evidence of firearm manufacturing involving a 3-D printer.

San Diego police said the teen was taken into custody on May 6 at Garfield High School without incident. Investigators said the student had a handgun tucked into his pants at the time of the arrest.

Authorities said they later searched the teen’s home and discovered evidence suggesting the manufacturing of several weapons, including ammunition and 3-D printed machine gun conversion devices.

Police also recovered a 3-D printer, carbon filament and a handgun magazine.

Firearms expert and trainer William Desy said the technology needed to manufacture firearm components is widely available.

“If you have a 3-D printer and you have some software, you can pretty much make anything you want to make,” Desy said.

Desy said restrictions on gun parts and unserialized weapons, commonly known as ghost guns, are not preventing some people from obtaining materials.

“If a 16-year-old has a car they can drive to Arizona and buy all the parts,” Desy said.

Desy said building a handgun with a 3-D printer is not complicated.

“I see a lower receiver for a handgun, a bag of ammunition, several lower receivers,” Desy said while discussing the evidence recovered.

In an e-mail to parents, Garfield High School Principal Guillermo Medina wrote that “bringing a firearm onto school campus results in an automatic recommendation for expulsion, and we will be pursuing that recommendation in this case.”

San Diego police spokesperson Ashley Nicholes said investigators acted quickly after receiving reports about the teen.

“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 said.

Investigators said the 16-year-old is suspected of supplying firearms to others and is also a suspect in a recent robbery at a trolley station.

Desy said the allegations raise additional concerns about firearms being distributed to other minors.

“If he is providing them to other juveniles, that is a huge problem,” Desy said.

Police urged parents to pay attention to changes in behavior and ask questions if something seems unusual.

“If they see something — a change in their child or unique behaviors that are not normal to them — pay attention and ask questions,” Nicholes said.

Police said the teen was booked into the Juvenile Detention Facility on several charges, including robbery, illegal gun possession and gun manufacturing.

This story was originally reported for broadcast by NBC San Diego. AI tools helped convert the story to a digital article, and an NBC San Diego journalist edited the article for publication.