CEO killing suspect Luigi Mangione expected to waive extradition and return to NYC: sources

NEW YORK -- Luigi Mangione, the accused killer of UnitedHealthcare CEO Brian Thompson, almost certain to waive extradition from Pennsylvania, where he was arrested a week ago, sources told ABC News.

Magione is slated to appear in a Pennsylvania court on Thursday, where the court will consider extradition. He is expected to waive extradition during his hearing.

Mangione remains in custody at a Pennsylvania state prison. A preliminary hearing on the Pennsylvania charges Mangione faces has been moved to Thursday, ACB News confirmed.

Mangione was apprehended at a McDonald's in Altoona, Pennsylvania, on Dec. 9 after nearly one week on the run. He's accused of gunning down Thompson outside a Midtown Manhattan hotel on Dec. 4 as the CEO headed to an investors conference.

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"Just a cold-blooded, horrible killing," President-elect Donald Trump said at a news conference Monday.

Thompson's murder ignited online anger at the health insurance industry. Many people online have celebrated the suspect and some have donated to a defense fund for Mangione.

"It's really terrible that some people seem to admire him, like him," Trump said.

"It seems that there's a certain appetite for him. I don't get it," Trump added.

Sources said writings police seized from Mangione suggest he was fixated on UnitedHealthcare for months and gradually developed a plan to kill the CEO.

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Among the writings recovered from Mangione was a passage that allegedly said, "What do you do? You whack the CEO at the annual parasitic bean-counter convention," according to law enforcement officials.

Neither Mangione nor his parents received insurance through UnitedHealthcare, the company said.

In Pennsylvania, Mangione faces charges including allegedly possessing an untraceable ghost gun. In New York, he faces charges including second-degree murder.

Mangione has hired Karen Friedman Agnifilo, a former member of the Manhattan District Attorney's Office, as his lawyer in New York.

FBI agents and NYPD detectives spoke to Mangione's mother the day before his Dec. 9 arrest after San Francisco police informed them she had filed a missing persons report and Mangione's photo seemed to match the suspect photo, law enforcement sources told ABC News. Mangione's mother told the New York investigators that the person in the widely shared surveillance images could be her 26-year-old son, sources said.