They’re 3D-printed or assembled piece by piece. A patchwork of state and federal regulations puts them in a legal gray area.

The man charged with murdering UnitedHealth Group Inc. executive Brian Thompson on a Manhattan sidewalk last week was arrested with a “ghost gun” in his backpack, refocusing attention on the hard-to-trace weapons and their lethal power.

The Maine Gun Safety Coalition is asking state lawmakers to ban ghost guns after an untraceable firearm was used by the alleged UnitedHealthcare CEO shooter. Firearms known as “ghost guns” do not have a serial number as they are usually constructed at home with a kit or with the assembly of separate pieces.

Israeli attacks across the Gaza Strip killed at least 33 Palestinians on Wednesday, most of them in an airstrike on a house in Beit Lahiya town on the northern edge of the enclave, medics said.

The man suspected of the fatal shooting of UnitedHealthcare CEO Brian Thompson was carrying a “ghost gun” — a type of untraceable, homemade firearm — when he was apprehended Monday, police said

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.