NEW YORK -- Luigi Mangione, the man accused of gunning down UnitedHealthcare CEO Brian Thompson, yelled to the press about "an insult to the intelligence of the American people" as he was physically dragged into the Blair County Courthouse in Pennsylvania on Tuesday.

The 26-year-old, who was shackled at the waist and ankles, was brought to court for an extradition hearing in connection with Thompson's Dec. 4 slaying outside a Midtown Manhattan hotel.

Mangione, who was arrested in Pennsylvania for gun possession on Monday and faces charges in New York including second-degree murder, is challenging his extradition.

"He has constitutional rights and that's what he's doing," his attorney, Thomas Dickey, told reporters.

At one point during Tuesday's court appearance, Mangione tried to interject, while his attorney, Thomas Dickey, was attempting to convince the judge to release him on bail. He was discussing the $8,000 in U.S. currency and $2,000 in foreign currency Mangione was allegedly found with. Dickey instructed his client, "Don't say a word."

The judge ordered Mangione held without bail.

The Manhattan District Attorney's Office said it will seek a governor's warrant to try to force Mangione's extradition. New York Gov. Kathy Hochul said in a statement that she'll sign a request for the governor's warrant "to ensure this individual is tried and held accountable."

Dickey told reporters Mangione will plead not guilty to the Pennsylvania charges.

The attorney said he has limited information about the facts of the New York murder case but he conceded Mangione is "accused of some serious matters." He added that Mangione is "taking it as well as he can."

Dickey declined to answer when asked if Mangione has been in touch with his family.

Mangione's mother filed in November a missing person report in San Francisco, seeking info on Mangione, according to two law enforcement sources. Repeated requests for information about the report went unanswered by the San Francisco Police Department. Both the chief and the spokesman referred questions to the NYPD.

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When Mangione was arrested on Monday he had "written admissions about the crime" with him, according to the New York arrest warrant.

Mangione had several handwritten pages on him that expressed a "disdain for corporate America" and indicated "he's frustrated with the health care system in the United States," NYPD Chief of Detective Joe Kenny told ABC News' "Good Morning America" on Tuesday.

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Mangione's writings, obtained by ABC News, addressed to the "Feds," said, "I do apologize for any strife of traumas but it had to be done. Frankly, these parasites simply had it coming."

He claimed that the U.S. has the most expensive health care system in the world, but ranks about No. 42 in life expectancy. He said UnitedHealthcare "has grown and grown, but as our life expectancy? No the reality is, these [ indecipherable ] have simply gotten too powerful, and they continue to abuse our country for immense profit."

Mangione appears to have been inspired by the Unabomber, according to an NYPD intel analysis report obtained by ABC News.

The report warned that like Ted Kaczynski -- whose 17-year bombing campaign killed three and injured 23 people -- Mangione may become a "martyr" who inspires "a wide range of extremists" to act.

Mangione "appeared to view the targeted killing ... as a symbolic takedown and a direct challenge to its alleged corruption and 'power games,'" according to a confidential assessment of the crime by the NYPD intelligence bureau described to ABC News.

Whether Mangione has a personal connection to UnitedHealthcare is unknown, NYPD Commissioner Jessica Tisch said.

A UnitedHealth Group spokesperson said in a statement, "Our hope is that today's apprehension brings some relief to Brian's family, friends, colleagues and the many others affected by this unspeakable tragedy. We thank law enforcement and will continue to work with them on this investigation."

Mangione was arrested in Altoona, Pennsylvania, on Monday in connection with Thompson's Dec. 4 slaying.

The NYPD was "thrilled" to get the call from Altoona police that they had a person of interest in custody, Tisch told "GMA."

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Kenny said "the key to this case" was releasing photos of the suspect's face to the media and the public.

"That picture reached Pennsylvania," where Mangione was recognized at a McDonald's on Monday morning, Kenny said.

"We are grateful as a city to that person," Tisch said.

"We had collected early in the investigation some forensic evidence, some DNA evidence, some fingerprints, so we were very confident that we were ultimately going to get to the right person," Tisch added.

"We do have a lot of evidence in this case," Tisch told "GMA."

Mangione was apprehended "in possession of the same New Jersey fake identification that was used" to check into a hostel on New York's Upper West Side before Thompson was gunned down, she said.

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The gun Mangione was allegedly found with on Monday "looks very similar" to the gun used in the murder, "with a similar suppressor," Tisch said. "So there's a lot of reasons that we feel very strongly that he is the person of interest."

Officers allegedly found a 3D printed pistol and a 3D printed silencer, according to the criminal complaint filed in Pennsylvania.

"The pistol had one loaded Glock magazine with six nine-millimeter full metal jack rounds. There was also one loose nine-millimeter hollow point round," the complaint said.

Kenny described the weapon as a "ghost gun," meaning it had no serial number and was untraceable.

Mangione, a Maryland native and Ivy League graduate, has been charged in New York with second-degree murder, possession of a loaded firearm, possession of a forged instrument and criminal possession of a weapon.

He was charged with five crimes in Pennsylvania, including carrying a gun without a license, forgery, falsely identifying himself to authorities and possessing "instruments of crime," according to the criminal complaint.

Mangione's family said in a statement that they're "shocked and devastated by Luigi's arrest. We offer our prayers to the family of Brian Thompson and we ask people to pray for all involved."

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The Pennsylvania State Police is asking for the public's help piecing together Mangione's travel in Pennsylvania. Anyone with information is asked to call 1-800-4PA-TIPS.

Police are also looking at Mangione's travel at various points across the United States and out of the county within the past year, sources said.