The black pistol allegedly used by Luigi Mangione to shoot and kill Brian Thompson, the UnitedHealthcare chief executive, was a so-called ghost gun, a firearm made up of parts bought online and assembled at home.
These weapons are largely untraceable — hence the name — and can be built using 3D printers.
Experts say ghost guns are the fastest-growing gun safety problem in the US, where lax regulations make it easy for most Americans to acquire a firearm.
Ghost guns are firearms without serial numbers that are put together from parts purchased either as a kit or as separate pieces. They are just as lethal as licensed guns sold over the counter, whose serial numbers are traceable by authorities.
The frame and receiver components of