Article continues below advertisementLuigi Mangione has his supporters as he sits behind bars accused of the murder of United Healthcare CEO Brian Thompson, with one man going as far as to impersonate an FBI agent in an attempt to secure his release. Mark Anderson was arrested at MDC Brooklyn in New York the evening of Wednesday, January 28, after prison workers asked for his credentials, a reported. Article continues below advertisementLuigi Mangione Fan Arrested for Impersonating FBI AgentSource: MEGAA Minnesota native tried to break Luigi Mangione out of his New York prison cell.