Luigi Mangione was arrested Monday when he was spotted at a McDonald's in Altoona, Pa.
NEW YORK (WPVI) -- Authorities are retracing the steps of the UnitedHealthcare CEO shooting suspect who was arrested Monday after being spotted at a McDonald's in Altoona, Pennsylvania.
Late Monday night, authorities filed second-degree murder and other charges against 26-year-old Luigi Mangione in the shooting death of New York City CEO Brian Thompson.
In connection with his arrest in Pennsylvania, he is also facing several charges, including carrying a gun without a license, forgery, falsely identifying himself to authorities and possessing "instruments of crime," according to a criminal complaint.
Mangione, who was shackled at the waist and ankles, was brought to court for a hearing Tuesday, where he challenged his extradition to New York.
"He has constitutional rights and that's what he's doing," his attorney, Thomas Dickey, said.
Mangione was on a Greyhound bus traveling through Altoona on Monday morning, sources said, when he got off and walked into a McDonald's where a witness recognized him from the images of the suspect circulated by police.
Authorities said they're working to trace his movements from New York City to Pennsylvania.
Pennsylvania Gov. Josh Shapiro said Mangione was traveling between Philadelphia and Pittsburgh with stops in between, including in Altoona.
"We do have a good idea how he got from Philadelphia to Pittsburgh. But there are some gaps in time. And so before we start laying out, a timeline of his travel, we really need to work through all of that. And, and so we know that at some point, it is likely he was in a variety of locations across the state to include Philadelphia, Pittsburgh, and points in between," said Lt. Col. George Bivens of the Pennsylvania State Police.
Police said they are working to develop a full sense of his timeline in Pennsylvania and how long he has been in Altoona.
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The charging document alleges that Mangione lied about his identity to police and carried the ghost gun without a license.
When Altoona police asked him if he had ever been to New York City, Mangione started shaking, according to the charging document. He didn't answer the question directly, police said.
Mangione had a ghost gun capable of firing a 9 mm round and a suppressor, police said. The gun and suppressor were "consistent with the weapon used in the murder," NYPD Commissioner Jessica Tisch said. The gun "may have been made on a 3D printer," police said.
Mangione also had a three-page handwritten document "that speaks to his motivation and mindset," Tisch said.
"It does seem that he had some ill will toward corporate America," police said.
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Authorities are going through his writings more thoroughly to understand his motive.
Mangione also had multiple fake IDs with him, including a fake New Jersey ID matching the ID the suspect used to check into a hostel in New York City before the shooting, Tisch said.
He was carrying a U.S. passport that identified him as Luigi Mangione, police said.
Police said it appears Mangione, a 2020 graduate of the University of Pennsylvania in Philadelphia, acted alone and they did not have his name before now.
While a student, he was a member of Phi Kappa Psi. Many were left stunned at the Ivy League campus after learning about the charges.
"For the past five days people have been talking about the murder and then boom he's a Penn student," said student Denzel Perez.
"Very quickly people started to try to find how many degrees of separation from him. Everybody knows somebody who knows somebody who apparently was in the same class as him," said student Gabriel Vega.
On Monday, Shapiro thanked the individual at McDonald's "who acted as a hero."
"I want to ask all of our fellow Pennsylvanians to demonstrate the same type of thoughtfulness and courage and smarts as the individual at McDonald's did this morning and help law enforcement here in Pennsylvania as we continue with our investigation," Shapiro said during a press briefing Monday evening.
He also thanked the Altoona police who "acted swiftly" to apprehend Mangione.
Shapiro lamented how some online have celebrated rather than condemned Thompson's killing.
"I understand people have real frustration with our health care system," Shapiro said. "This killer is not a hero. He should not be hailed."
ABC News contributed to this report.