Police said Luigi Mangione, the man charged in the killing of UnitedHealthcare CEO Brian Thompson, appears to have had a ghost gun, a weapon that can be made using a 3D printer.

Investigators believe the gunman used a rare, integrally suppressed pistol, possibly a Brügger & Thomet Station Six.

Luigi Mangione, the suspect identified in the killing of UnitedHealthcare CEO Brian Thompson, used a “ghost gun,” according to police officials, a type of firearm typically assembled at home that is ...