The man accused of killing UnitedHealthcare's CEO has been charged with murder as an act of terrorism, prosecutors said Tuesday as they worked to bring him to a New York court from from a Pennsylvania jail.

Luigi Mangione already was charged with murder in the Dec. 4 killing of Brian Thompson, but the indictment could help move along procedural steps toward extraditing the suspect.

Mangione’s New York lawyer hasn’t commented on the case.

Thompson, 50, was shot dead on a Manhattan street as he walked to a hotel where Minnesota-based UnitedHealthcare - the United States' biggest medical insurer - was holding an investor conference.

After days of intense police searches and publicity, Mangione was arrested on Dec. 9 after being spotted in a McDonald's in Altoona, Pennsylvania. New York police officials have said Mangione was carrying the gun used in Thompson's killing, a passport and various fake IDs, including the one that the suspected shooter presented to check into a New York hostel.