Mark Anderson, 36, allegedly went to the Metropolitan Detention Center in Brooklyn on Jan. 28 posing as a federal agent and claimed to have a court order to release Mangione.
When Bureau of Prisons personnel asked to see Anderson's credentials, he showed them a Minnesota driver's license and "threw at the BOP officers numerous documents", according to federal prosecutors.
Officials said Anderson was also carrying a bag containing a barbecue fork and a pizza cutter.
Anderson has been charged with falsely impersonating a federal officer.
Mangione remains held at MDC-Brooklyn while awaiting federal and state trials for the assassination-style killing of UnitedHealthcare CEO Brian Thompson in December 2024.
SEE RELATED: Mangione speaks out in court as his state trial is tentatively set for June
----------
* Get Eyewitness News Delivered
* More Manhattan news
* Send us a news tip
* Download the abc7NY app for breaking news alerts
* Follow us on YouTube