Luigi Mangione, the 26-year-old tech whiz suspected of gunning down UnitedHealthcare CEO Brian Thompson last week, allegedly used a ghost gun that he might have made on a 3-D printer to commit the killing, authorities said.

“He was in possession of a ghost gun that had the capability of firing a 9-mm round and a suppressor,” NYPD Commissioner Jessica Tisch said at a Monday press briefing, adding that the piece “may have been made on a 3-D printer.”

Cops nabbed Mangione — who sources said is an anti-capitalist Ivy League grad who liked online quotes from “Unabomber’’ Ted Kaczynski — while he ate at a McDonald’s in Altoona, Pa., ending an intense manhunt that began after he executed Thompson outside a Manhattan hotel last week.

Originally from Towson, Md., Mangione may have hated the medical community because of how it treated a sick relative, sources said.

Aside from the untraceable, homemade gun, the former prep school valedictorian was caught with a silencer, a US passport, four fake IDs with names used during the killer’s stint in New York City and a two-and-a-half page manifesto, sources said.