The Glock-style pistol found with Luigi Mangione that was allegedly used to gun down health care CEO Brian Thompson began as ...

D-printed guns, such as the one allegedly used to kill UnitedHealthcare CEO Brian Thompson, are likely to become more common ...

but underscored the burgeoning 3D-printed variety. With those, DIY-gunmakers download a design file, and feed it into a machine that prints layers of plastic to make some components of a gun.