A 36-year-old man from Mankato, Minnesota, was arrested Wednesday after allegedly attempting to impersonate an FBI agent to gain access to Luigi Mangione, who is in custody at the Metropolitan Detention Center (MDC) in Brooklyn. Court documents and law enforcement officials say the suspect, Mark Anderson, claimed he had judicial authorization to release Mangione, who faces federal charges in connection with the December 2024 murder of UnitedHealthcare CEO Brian Thompson in Manhattan.

According to an affidavit unsealed Thursday, Anderson approached the MDC intake area and told officers he was an FBI agent in possession of paperwork “signed by a Judge” authorizing the release of a specific inmate. When asked for identification, Anderson presented a Minnesota driver’s license and asserted he was armed. He also displayed and tossed several documents at Bureau of Prisons officers, which allegedly related to legal claims against the Department of Justice.

In addition to impersonating federal law enforcement, Anderson reportedly told authorities he wanted to be arrested and claimed that the Mexico-based Jalisco New Generation cartel was pursuing him. Law enforcement sources emphasize that there is no indication Mangione had any knowledge of Anderson’s attempted actions.

Following his detention, a search of Anderson’s backpack revealed a large barbecue-style fork and a round steel blade, which were noted in the court filings. Anderson is currently being held in the MDC’s Special Housing Unit while federal investigators continue to examine the case.

Luigi Mangione’s Case Background

Mangione, a Brooklyn resident, is awaiting trial for the alleged murder of Brian Thompson, who was shot on a Manhattan street in December 2024. Federal prosecutors recently set September 8, 2026, as the date for the start of jury selection. Mangione has pleaded not guilty, and the investigation into the murder remains ongoing.

Authorities say Anderson had traveled from Minnesota to New York for a potential employment opportunity that did not materialize. He has reportedly been working in a local pizzeria since arriving in Brooklyn. Law enforcement officials are reviewing Anderson’s motives and whether any further criminal charges could apply in addition to impersonating a federal officer.

The Brooklyn MDC houses federal inmates pending trial and serves as a central intake facility for the New York City area. Security measures include verifying official documentation, checking credentials, and screening individuals attempting to gain access to inmates. Officers say Anderson’s attempt to use false credentials highlights ongoing concerns regarding impersonation of law enforcement and security protocols at federal detention centers.

Legal Implications and Federal Oversight

Impersonating a federal officer is a serious federal crime, carrying potential penalties including imprisonment and fines. Prosecutors note that such acts can compromise the integrity of federal detention procedures and place both staff and inmates at risk. Anderson’s case will likely be prosecuted in federal court, with the Department of Justice overseeing the investigation alongside the FBI.

Law enforcement sources stress that incidents like these, while rare, underscore the need for vigilance in detention facilities and clear verification protocols. Anderson’s claim that a cartel was pursuing him appears to be unsubstantiated, and investigators are examining all evidence in connection with his actions.

Next Steps

Anderson remains in custody as federal authorities continue their investigation. Mangione’s trial preparations are underway, and security measures at the MDC have reportedly been reviewed to prevent similar attempts. Officials also continue to assess the broader implications of impersonation attempts and potential risks to federal detention operations in New York.