Luigi Mangione has been formally indicted in New York on first-degree murder charges for the fatal shooting of UnitedHealth Group executive Brian Thompson outside a midtown Manhattan hotel.

The case was elevated to first-degree murder because Thompson was killed "in furtherance of an act of terrorism,” prosecutors said Tuesday in New York. Mangione faces as long as life in prison without the possibility of parole if he is convicted.

Mangione, 26, fled Manhattan after the Dec. 4 shooting, authorities said, touching off a five-day manhunt that ended with his arrest in western Pennsylvania. He waited outside the New York hotel with a 9mm 3D-printed ghost gun, prosecutors said.