Home-gun-making pioneers and activists say the man accused of murdering UnitedHealthcare CEO Brian Thompson used a 3D-printed gun but wasn’t known to them, and they’re unsure why he went the homemade route.

The experts who spoke with The Reload said pictures of the attacker’s gun show the frame contains telltale signs of 3D printing, including visible layers and potential minor damage from where the builder removed it from the printer, rather than signs it was a more common pre-made but unfinished frame found in many homemade gun kits. While the shooter had to source the metal components of the pistol, such as the slide and barrel, he appears to have made the plastic frame from scratch.

“I can absolutely confirm it’s a 3D-printed frame with 100% certainty,” John, who goes by Mr.Snow.Makes on social media and is a prolific gun maker, told The Reload.

They identified a specific frame design that the shooter likely used as well. They agreed it was a variation on a design produced by an activist who goes by the name FreeMenDontAsk (FDMA).

“Of course, the images we have are blurry and suboptimal, but being very familiar with different frames-both 80% and printed-the relief around the mag catch and the angle under the trigger guard are distinctive,” Matt Larosiere, a gun-rights lawyer who works with 3D-printed gun designers and hobbyists, told The Reload. “That the grip texture is raised relative to the rest of the frame versus inletted is indicative of it being a certain remix (stylistic/ergonomic modification) of the DD19.2.”

“The file was released originally by Detterence Dispensed in Feb. 2021 in the FDMA DD19.2 file pack,” Snow said. “Specifically, this file is denoted as the CMW stipple mod.”

Rob Pincus, who organizes a shooting competition for homebuilt gun enthusiasts, agreed the frame is a DD19.2 but said it may have been “remixed” by somebody else. Cody Wilson, who owns Defense Distributed and became the first face of 3D-printed guns after unveiling The Liberator in 2013, identified the specific designer.

“I am certain the shooter used a variant of an FMDA Glock frame,” he told The Reload. “A ‘Chairmanwon‘ has taken credit for the cosmetic remix of this frame, which is a part of his V1 series and is/was promoted by Deterrence Dispensed/The Gatalog since 2021.”

While unserialized homemade firearms, often referred to as ‘ghost guns’ by law enforcement since they can’t trace them back to their point of sale, have become increasingly popular over the past decade, 3D-printing is a more difficult and less common process for making them. As such, it has remained a niche pursuit with a relatively tight-knit–though fiercely independent and sometimes fractious (Wilson and Larosiere are currently suing one another)–community. Although anonymity and resistance to government surveillance is a key

None of the enthusiasts said they’d ever encountered the shooter in person or online.

“I am unaware of him being involved in the 3D-printing world,” Pincus said. “I don’t recognize him from any social media or events.”

Larosiere said neither he nor anyone in the community he’s talked with recognized the shooter or his screen name.

“Given the age of this release, I doubt he was an active member in the overall 3D-printed space,” Snow said.

The experts also agreed the shooter didn’t need to be an expert to pull off the pistol build. While it may be easier to build a gun from a pre-made kit with an unfinished frame, like those made by the now-defunct company Polymer80, the skill level required to print the pistol frame in question isn’t that advanced. It wouldn’t be that expensive either.

“It requires being able to use a 3D printer, files, and hand drills at a pedestrian level of competency,” Larosiere said.

“This wouldn’t require a high level of skill with a good hobby printer,” Snow said. “The frame would be ‘plug and play’ at the $1000 level, well within his financial resources. Assembling the gun with traditionally manufactured parts would also be a low-skill level mechanical/handyman operation.”

Wilson said the tech and free online guides are now “good enough that a total novice can jump in and successfully print and build these items,” including the silencer/sound suppressor the shooter allegedly used.

But there wasn’t a consensus around why the shooter decided to use a 3D-printed gun. Pinncus noted there hadn’t been reports that the suspect had a criminal record serious enough to prevent him from buying a factory-made gun through traditional channels. Additionally, Snow said that while printing your own gun parts is not exorbitantly expensive, it is usually more expensive than buying a mass-produced gun.

The experts said 3D-printed guns tend to require more adjustment and breaking in to function properly. So, they are often less reliable than their factory-made counterparts. That, they said, could explain why he appeared to have so much trouble operating his gun during the attack, leaving numerous live rounds behind as he tried to clear multiple malfunctions.

“I do think the failures are related to the 3D printed build and cheap slide,” Wilson said. “I’ve seen devs and enthusiasts assess that his slide didn’t fit well and that he didn’t iron out those kinds of fitment issues before he used the gun.”

Pincus, Snow, and Larosiere said the suppressor the suspect used was also probably misconfigured.

“We haven’t seen the suppressor yet, but the ‘malfunctions’ appear to be the ordinary result of shooting a tilting-barrel handgun without a Nielsen device (also known as recoil booster or linear decoupled),” Larosiere said. “Even with a factory Clock and factory direct-thread suppressor, the slide will not cycle enough to load another round without a Nielsen device due to the weight of the suppressor tending to keep the barrel locked. Most suppressors designed for tilting barrel handguns have such a device equipped, but most printed suppressor designs are direct-thread, in that the suppressor simply threads to the barrel with no intermediary.”

Although, Pincus said that may have been by design.

“It is, however, possible that this was a Feature, not a Flaw,” he said. “He may have wanted to be sure his inscribed cases were dropped close to the body and not ejected where they might not have been found.”

Snow said the shooter going out of his way to avoid buying a serialized gun makes it rational to think he was avoiding a paper trail. But Pincus said the brazen nature of the killing and numerous breadcrumbs the suspect left behind make it unlikely he was trying to avoid a paper trail.

“It’s always hard to try to guess the ‘logic’ of a person who does something like this, but I think the fact that this guy both wasn’t prohibited from buying guns AND wasn’t trying to be/remain hidden in any significant way undermines the idea that he used a 3D-printed gun for any reason tied to avoiding a paper trail or serial number,” he said.

He and Wilson said some of the shooter’s alleged writing indicates the methods of another notorious killer may have inspired him.

“Reports from his writings and a ‘book club’ he was part of indicate that he was enamored with the Unabomber, who was a DIY guy. He may have been trying to be more like his ‘hero,'” Pincus said.

However, Wilson said the explanation may be more mundane than that.

“Because he’s been connected to reading Ted Kaczynski and made at least a superficial political statement by the assassination, it’s tempting to see his use of a 3D pistol as intentionally political,” he said. “My read is that he was experiencing some kind of mental disarray or decline. ”

Additionally, all the experts said it’s possible the shooter wasn’t sending any kind of message by using a 3D-printed gun. Snow and Larosiere argued he could have simply bought the gun from somebody else. Wilson and Larosiere said it could have just been a byproduct of the suspect’s apparent interest in tech and computer programming.

“He may have been exposed to 3D guns months or years before this killing, and the gun might have just been convenient or on hand,” Wilson said.