Ghost guns, like the weapon the NYPD said UnitedHealthcare shooting suspect Luigi Mangione had when arrested, can be assembled at home.

A homicide investigator typically uses ballistics and serial numbers of weapons checked via a vast network of gun shop records, manufacturer IDs and crime databases. But those sleuthing tactics are fast becoming old-school science as a new era of weapons increasingly hits the nation's streets: untraceable 3D-printed guns and silencers like the ones found this week on suspected killer Luigi Mangione.

Police believe the brazen killing of UnitedHealthcare’s CEO was carried out with a ghost gun. The nearly untraceable weapons can be made a home.