Luigi Mangione, the man accused of fatally shooting UnitedHealthcare CEO Brian Thompson, was extradited from Pennsylvania to New York on Thursday. Mangione waved his preliminary hearing and extradition on Thursday morning in Pennsylvania, where he was arrested and charged with firearms and forgery offenses. After being flown into lower Manhattan on a helicopter, Mangione appeared in court and his attorney did not request bail.Mangione, who already faced state murder charges, learned on Thursday that he is also being charged with a federal count of murder through use of a firearm, as well as stalking and other crimes. Court documents filed Thursday allege Mangione was found in possession of a loaded 9 mm pistol and silencer consistent with the weapon used to kill Thompson; clothing that matched appeal worn by the shooter during Thompson's killing; an envelope with several thousand dollars; and a letter addressed "To the Feds."A notebook with troubling passages was also found, according to court documents. Investigators said the entries described details as "finally coming together and the target is insurance because it checks every box. There's also an entry, the court document states, that describes an intent to wack the CEO of one of the insurance companies. RELATED STORY | Assassination of a CEO: A Court TV & Scripps News Special ReportBefore federal charges were filed Thursday, Mangione's attorney addressed media reports citing sources about the expected charges."The federal government's reported decision to pile on top of an already overcharged first-degree murder and state terror case is highly unusual and raises serious constitutional and statutory double jeopardy concerns," said attorney Karen Friedman Agnifilo. "We are ready to fight these charges in whatever court they are brought."The case has drawn attention from across the U.S. as the nation's health care system faces much criticism. Several supporters of Mangione showed up outside the Altoona, Pennsylvania, courthouse with some arriving dressed as Luigi from the Super Mario Bros. video games.