Authorities arrested a person of interest in the murder of UnitedHealthcare CEO Brian Thompson in Pennsylvania on Monday, identifying the individual as Luigi Mangione. He was charged late Monday.

Mangione, 26, was spotted at a McDonald's in Altoona, Pa., New York City Police Commissioner Jessica Tisch said during a news conference. Officers questioned Mangione and found he was carrying several fake IDs and a U.S. passport, a gun and a firearm suppressor similar to the one used in the murder, she said.

Mangione was "sitting and eating" in the McDonald's on Monday morning when he was identified by an employee, said Joseph Kenny, chief of detectives with the New York Police Department.

Police found a three-page handwritten document that allegedly spoke to the suspect's motivation in the killing and his mindset. The document criticized health care companies for putting profits above care, according to the New York Times.

Kenny said the manifesto did not target other individuals, but it did convey a dislike for corporate society.

"It does seem he has some ill will toward corporate America," he said.

An NYPD report said Mangione may inspire other acts of violence.

"Based on observed initial online reactions to the shooting, including celebrations of the killing of a health insurance executive, there is a risk that a wide range of extremists may view Mangione as a martyr and an example to follow," the NYPD report said, according to the New York Times.

The recovered firearm was a 9mm "ghost gun," which may have been made with a 3D printer, Kenny said.

On Monday night, New York prosecutors filed murder and other charges against Mangione. In Pennsylvania, his charges included possession of an unlicensed firearm, forgery and providing false identification to police.

Mangione's last known address was Honolulu, Hawaii, according to Kenny. But he was born and raised in Maryland and also has ties to San Francisco.

Mangione was high school valedictorian at the all-boys Gilman School in Baltimore. High school tuition at Gilman is $37,690, according to the school's admissions page.

In a message emailed to Gilman families on Monday, Head of School Henry Smyth said the school is aware that Mangione has been linked to the shooting. His email confirmed that Mangione graduated from Gilman with the class of 2016.

"This is deeply distressing news on top of an already awful situation," Smyth wrote in the email. "Our hearts go out to everyone affected."

In 2020, Mangione received his bachelor's degree with a major in computer science and minor in mathematics as well as a master's degree in computer and information science from the University of Pennsylvania, according to a Penn spokesman.

While a LinkedIn account says he works as a data engineer at California-based auto marketplace TrueCar, a company spokesman confirmed Mangione has not worked there since 2023.

On what appears to be Mangione's social media accounts, he posted photos from travels with friends over the years. On an X page, there is an X-ray image in his header photo.

On the book review platform Goodreads, it showed someone named Luigi Mangione read several books on dealing with back pain, including "Back in Control: A Spine Surgeon's Roadmap Out of Chronic Pain" and "Healing Back Pain: The Mind-Body Connection."

On the GoodReads page, that person left a detailed 4-star book review in January for "Industrial Society and Its Future" by Theodore John Kaczynski, the mail bomber commonly known as the Unabomber. Mangione wrote that it is too easy to write off the book "as the manifesto of a lunatic."

"He was a violent individual — rightfully imprisoned — who maimed innocent people. While these actions tend to be characterized as those of a crazy luddite, however, they are more accurately seen as those of an extreme political revolutionary," Mangione wrote.

Thompson lived in Maple Grove with his wife, Paulette, and their two teenage sons. He worked at UnitedHealthcare for 20 years and was named its CEO in 2021. The Minnesota Star Tribune reported this year that Thompson was among the state's top-paid executives with a total compensation of $9.1 million.

Staff writers Eder Campuzano and Paul Walsh contributed to this story. The Associated Press contributed to this story.