NEW YORK (WABC) – Luigi Mangione, the suspect accused of shooting UnitedHealthcare CEO Brian Thompson, left New York City by train rather than by bus as initially thought, police sources told ABC News.

Investigators initially believed Mangione had boarded a bus at the Port Authority terminal at the George Washington Bridge, where he was seen on surveillance cameras as a taxi dropped him off, according to investigators. There was no picture of Mangione actually getting on a bus.

Now, police sources say there is video evidence showing Mangione left the George Washington Bridge bus station, headed south to Penn Station and left New York City by train for Philadelphia.

Pennsylvania authorities said Mangione then spent several days crossing the state from Philadelphia to Pittsburgh.

Mangione was arrested Monday in Altoona, Pennsylvania, after being on the run for nearly a week following the Dec. 4 killing.

Mangione, 26, is being held at a Pennsylvania state prison after a judge denied him bail on Tuesday.

In Pennsylvania, Mangione is charged with, among other things, the alleged possession of an untraceable ghost weapon. In New York, he is charged with, among other things, second-degree murder.

Mangione could waive extradition to New York City as early as Tuesday, Manhattan District Attorney Alvin Bragg said Friday.

“There are indications that the defendant may waive it, but that waiver is not complete until a trial,” Bragg said.

A trial in Pennsylvania could be scheduled for Tuesday at the earliest, Bragg said.

“So until then, we will continue to move forward on parallel paths. We will be ready whether he waives extradition or whether he challenges extradition,” the prosecutor said.

Mayor Eric Adams said Friday that Mangione was radicalized at the University of Pennsylvania.

“Here you have a young man who went to an Ivy League school, came from a wealthy background and family, and had all the things that many Americans would like to have. But he found he hated corporations and other things,” Adams said on GMGT Live’s “The Reset Talk Show.” “We are radicalizing our children in general, but specifically on these Ivy League campuses.”

Adams attributed the support Mangione is receiving to “anger and pain.”

“People know how difficult it is to navigate our healthcare system on many levels, how high the costs of the healthcare system are. Some of the denials, some of the illnesses that aren’t covered. And all across America, people have experienced this disappointment. And you too.” “We’re seeing a reaction to that,” Adams said. “And we can’t signal that if you’re angry about something, if you’re angry because you got a ticket, you’re going to react with violence.”

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It became known that Mangione was not a member of the insurer, said a company spokesman.

“Brian Thompson’s killer was not a member of UnitedHealthcare,” the company told ABC News.

Prosecutors in the Manhattan District Attorney’s Office have begun presenting evidence to a grand jury as they work to secure an indictment against Mangione in Thompson’s killing, sources told ABC News.

The 26-year-old Ivy League graduate remains in custody at a Pennsylvania state prison after a judge denied him bail on Tuesday. His next court date in Pennsylvania is December 30.

“He has constitutional rights and that’s what he’s doing” by challenging interstate transfer, defense attorney Thomas Dickey told reporters Tuesday.

Authorities are still trying to access a phone that police found in an alley after the shooting and is believed to be connected to the suspect, sources said Thursday. Sources said police obtained a search warrant for the phone.

RELATED | Killing of UnitedHealthcare CEO: New York prosecutors present evidence to grand jury, sources say

At least two additional search warrants have been issued so far in the New York case. That included a search of the hostel where the suspect was staying in New York, as well as a search of the backpack containing Monopoly money and a jacket found in Central Park that was believed to belong to him, sources said.

On Friday, the FBI’s New York field office said it had passed on a tip from San Francisco police, who said they recognized the suspected Midtown shooter from an earlier missing person report filed by his mother.

“The FBI New York conducted routine investigative activities and forwarded this and other tips to the New York City Police Department as part of our assistance in their investigation,” FBI New York said in a statement. “The extensive sharing of the photos by law enforcement led to the identification of a citizen and subsequent arrest by the Altoona Police Department.”

An NYPD official says the FBI shared general information about Mangione’s possible identity, but not in an urgent manner or in a way that would establish it as a credible lead from the San Francisco Police Department.

The NYPD previously said it received no information about Mangione’s identity before his capture in Altoona, Pennsylvania.

Three bullet casings found outside the midtown Manhattan hotel where Thompson was fatally shot match the gun allegedly found on Mangione when he was arrested, police announced Wednesday.

According to police, fingerprints from a water bottle and a Kind Bar near the crime scene were also linked to Mangione.

Meanwhile, the search for the e-bike Mangione abandoned as he fled the shooting last week was never found.

Mangione left the bike on the Upper West Side after the murder and hailed a taxi at 86th Street and Amsterdam Avenue to the George Washington Bridge bus station.

One working theory is that someone discovered it abandoned and stole it.

RELATED | Timeline of the shooting of UnitedHealthcare’s CEO

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