NEW YORK, United States (AFP) — A man was charged Thursday after allegedly posing as an FBI agent at a United States (US) jail to try to free Luigi Mangione, the suspect in the high-profile murder of a health insurance executive.

Mark Anderson, 36, was arrested late Wednesday after New York prison staff asked to see credentials and he could only produce his driver’s license before claiming to have weapons on him, according to court filings.

Officials found a large barbeque fork and a round steel blade — which resembled a pizza cutter — inside Anderson’s backpack.

The criminal complaint said Anderson told staff at the Metropolitan Detention Center in Brooklyn that he had paperwork “signed by a judge” authorising the release of a specific inmate, unnamed in the filing.

A judicial source confirmed the inmate was Mangione, the 27-year-old accused of gunning down UnitedHealthcare CEO Brian Thompson in December 2024.

Thompson’s killing, which was captured on surveillance video, shocked Americans and exposed public anger with the country’s profit-driven private healthcare system.

Mangione is charged at the federal and state level. He has pleaded not guilty in both cases.

His federal trial is set to begin with jury selection on September 8. A date has yet to be set in the state case.