BERLIN (DPA) - When a right-wing extremist in combat gear tried to break into a synagogue in the eastern German city of Halle earlier this week to massacre Jewish worshippers, his weapons repeatedly failed him.
In video footage taken by a camera mounted on his helmet and posted online, Stephan B - whose full name has been withheld - is heard shouting as his weapons fail to fire.
"What's wrong? Jesus, man, load! Oh, shit!" he says.
If he had managed to break into the synagogue's side door and reach the 50-strong congregation inside, the death toll would very likely have been far higher. Instead, Stephan B murdered two bystanders and injured several others nearby.
In the so-called manifesto the attacker uploaded to Kohlchan - the German counterpart to controversial US platform 8chan - he describes his hand-assembled weapons arsenal in detail.
One of them was a "Luty SMG 9mm Parabellum", designed by Philip Luty, a gun rights activist who devoted his life to publicizing blueprints for making firearms from easy-to-obtain materials.
Another of his Luty-inspired firearms was partially made up of pieces of plastic that can be created in a 3D printer. The arsenal also contained other homemade guns and hand grenades.
Investigators later discovered a 3D printer in Stephan B's home.
The sequence of events has raised fears in Germany that terrorists may be turning to 3D printed guns in a country that has some of the strictest gun laws in the world.
The technology, which has been hailed as the future of manufacturing, works by building up layer upon layer of material - often plastic, but also metal - to build complex solid objects.
The risks of using homemade weapons are higher than professionally made guns. Not only could they fail to fire, they could potentially misfire and cause injury to the shooter.
Aware of the possible criminal uses of their products, the manufacturers of 3D printers have tried to stop the illicit printing of weapons. Matthieu Regnier, co-founder of 3D printer company Dagoma, says his company distributes manipulated gun manuals to deter criminals.
"The weapon files that we change look just like the original, but the finished printed products are not usable," says Regnier, adding that the "false" manuals have been downloaded a staggering 13,000 times.