When Luigi Mangione was arrested at a McDonalds in Altoona, Pa., in the December 4 killing of UnitedHealthcare CEO Brian Thompson, he had in his possession a black handgun and a black silencer. Those might not have been extraordinary findings for a suspected assassin—except for the fact that his gun and silencer weren’t bought at a store or a gun show, with serial numbers that could be easily traced by authorities. They were manufactured by a 3D printer, meaning they had no serial numbers and were completely untraceable. And while that might once have seemed a remarkable technological achievement, those days are gone.

In recent years, statistics show that arrests related to 3D-printed guns have tripled, and in 2022 federal officials recovered more than 25,000 homemade guns. And these are no toy guns. After Mangione’s arrest, members of the Altoona police department wrote in the criminal complaint that the weapon had “a metal slide and a plastic handle with a metal threaded barrel.” And it had one loaded Glock magazine with six nine-millimeter full metal jacket rounds.

And from a USA Today headline: 3D-printed weapons are turning “America into the Wild West.”

“This is old news, 3D printed guns. This has been known for 8 to 10 years,” says Stephen Chomyszak, a professor of the practice of mechanical engineering at the College of Engineering and director of BU’s 15,000-square-foot Engineering Product Innovation Center (EPIC), home to 25 3D printers. “This is not new or revolutionary, but it’s sensational because of the victim in this case. Evil people will find any way they can to carry out their evil deeds.”

The rapidly increased ability of 3D home printers—now available for purchase for less than $1,000—have not only made it easier for seasoned engineers to print work projects and for college students to print class projects, but also made it possible for people to print sophisticated weapons.

Tom Chittum, a former associate deputy director of the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives, said after the New York City shooting of Thompson that “if the gun used in the New York assassination really was 3-D printed, it would certainly be the highest-profile crime ever committed with one, and it would be one of a small number overall.”

EPIC’s rules are clear—no weapons

Boston University students have access to an impressive collection of 3D printers at the recently modernized EPIC. “We have sculpture students, architecture students, archaeology students, BU Academy students, Questrom students—they all come into EPIC and use the printers,” says Kara Mogensen, one of EPIC’s full-time lab supervisors. “We have online training for our self-service printers, and we also offer events involving 3D printing.” 

But in recent years there’s been growing conversations about what can, and more important, cannot be printed on a 3D printer, not just at Boston University, but anywhere. “There have definitely been discussions [here] about what is allowed to print, and obviously weapons are not allowed,” Mogensen says. On the EPIC website, under Policies and Prioritization, it’s listed clearly under “What We Can’t Help With”: “The production of, maintenance of, or modification of any weapons or knives.”

Nationwide, there are no required background checks to be passed before a person downloads a blueprint or component parts to make a 3D-printed firearm. And because a 3D-printed gun, or a ghost gun, has no serial number and is sculpted from a digital model, or an inexpensive kit purchased online, it’s impossible for authorities to trace its origin. Massachusetts is one of the strictest states when it comes to regulating 3D-printed firearms. “Massachusetts also prohibits the manufacturing, distributing, possessing, or selling of any firearm or ammunition undetectable by metal detectors or X-ray machines,” according to 3Dprint.com.

But writing a regulation to prevent a behavior and actually stopping that behavior altogether are two separate things.

“Quality, reliability, speed, cost, the 3D printers today check off all four of those boxes, and that means anybody with $1,000 can buy one to print a weapon,” Chomyszak says. “The world is not perfect, but it’s more good than it is bad. If we stop progress for the sake of a few evil, bad players in the world, at the expense of all the good in the world, that’s a bad tradeoff.”

Chomyszak says that while 3D printing has been around since the 1980s, big, highly sophisticated machines, like some of those at EPIC, are unattainable to the average consumer. EPIC opened in 2014 with three printers, and in the last decade, he says, the technology has become more affordable as machines have gotten smaller and cheaper.

The demand at EPIC for use of the printers has grown tremendously, he says, and it’s now an important tool for coursework, research, and for personal projects.

Making it easy to put together a ghost gun

One reason for the growth in popularity and use of 3D printers is in the materials they can print. The traditional substance used, called PLA, is a filament made mostly of corn, and is a plastic-like material that’s also combustible. It’s not durable, however, so it can’t make many things that are functional or with moving parts, other than something small like a paper clip. That’s why the early days of 3D printing focused on designing small models or toys or game characters.

Today’s modernized 3D printers can print a polycarbonate material, or nylon, or even glass, giving them the ability to make stronger, durable, moveable items. 

“My first experience with 3D printers was at EPIC, and our printers back then were old, very slow, very sensitive, and there was a high cost for the filament,” Mogensen says. “Now we have more affordable printers, we are allowing students to use them, we’re less worried about material usage. The printers are now under $1,000 and the software is more intuitive, and they have more sensors that will pause the print if something is going wrong.”

The challenge for monitoring what’s being printed on a 3D printer is that while it’s easy to recognize if a complete weapon is emerging, it’s much harder to identify if only a small part of a weapon is being printed. “How do I tell if it’s a weapon or an accessory for a weapon?” Mogensen says. “It’s been in discussions for several years now. That was the concern, not printing a full weapon.”

And with the market of people selling designs completely unregulated, it makes it easy for someone to put together a ghost gun.

Mogensen says it’s important to emphasize the value that 3D printers bring to an educational setting to get projects done quickly. “You can have your model in front of you to modify and improve it,” she says. “It’s definitely been good for our engineering students to make prototypes and finished parts. We have a lot of students that come in that need to make a design project. They make little design cars [for instance] that they can program and follow on a track.”

The ability to print a project in four hours is “a huge benefit,” she says. She recalls one group making ice cream scoops and how quickly they were able to print the design with a hollowed scoop shape. And when it wasn’t perfect, they made a few edits, and printed a new one. “It’s all about having it in your hands quickly,” she says.

Now authorities are investigating if the same type of 3D printing speed and efficiency that helps BU students make ice cream scoops is what motivated the suspect in the UnitedHealthcare murder to use that same technology. According to reports, a handwritten document Mangione was found with describes the difficulty of planning the shooting as “fairly trivial,” because it required only “basic CAD.” CAD is the commonly used computer-aided software program used in most 3D printing jobs.