By Yisroel R.

A 36-year-old man accused of pretending to be an FBI agent in an attempt to free Luigi Mangione from prison pleaded not guilty Tuesday in Brooklyn federal court to falsely posing as a government officer.

Mangione is the man charged with killing UnitedHealthcare CEO Brian Thompson in December 2024 outside a Midtown Manhattan hotel. He is currently being held at the Metropolitan Detention Center in Brooklyn while awaiting trial in both federal and state cases.

According to federal prosecutors, the defendant, identified as Mark Anderson, went to the detention center claiming he was a federal agent and said he had paperwork signed by a judge authorizing the release of someone in custody. Prosecutors say he threw papers at jail staff and told them he had weapons in his bag.

When officers searched the bag, they found a pizza cutter and a barbecue fork. Authorities say the person Anderson was attempting to release was Mangione.

Anderson appeared in court for a brief arraignment, and a judge ordered that he remain in custody pending further proceedings.

Mangione faces federal stalking charges, along with state murder and weapons charges related to the fatal shooting. He has pleaded not guilty in both cases and remains detained as he awaits trial later this year. His case has drawn national attention, with some supporters portraying Mangione as someone who took a stance against corporate insurance greed.