A suspect in connection with the killing of UnitedHealthcare CEO Brian Thompson was arrested in Pennsylvania on Monday in possession of a gun and multiple fake IDs, officials said.

Luigi Mangione, 26, was arrested at a McDonald’s in Altoona after a customer recognized him from photos that were distributed during the days-long manhunt that followed Thompson’s death, police said.

He was arraigned Monday evening in Pennsylvania on two felony charges — forgery and carrying a firearm without a license — and three misdemeanors: tampering with records or identification, possessing instruments of crime and providing false identification to law enforcement.

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He was denied bail and did not enter a plea. Officials said they expect charges connected to Thompson’s death last week to be filed in New York “very soon.”

Law enforcement officials said officers immediately recognized Mangione as the person of interest in the fatal shooting of Thompson after they asked him to pull down his mask.

When they asked him whether he had recently been to New York, “the male became quiet and started to shake,” the police complaint says.

Authorities said Monday night that while Mangione was initially cooperative, he was no longer being helpful.

Mangione was found with a gun similar to the one used in the shooting and had a fake ID with the same name the suspected gunman used at a New York City hostel, police said.

“Additionally, officers recovered a handwritten document that speaks to both his motivation and mindset,” New York City Police Commissioner Jessica Tisch said.

Mangione, who was born and raised in Maryland, has ties to San Francisco and had a last known address in Hawaii, officials said. He has no previous arrests.

The document speaking to a motive came in the form of three handwritten pages, evidence that is with Altoona police, New York City officials said.

It wasn’t immediately clear whether the pages named Thompson.

Investigators are also looking at Mangione’s online posts about domestic terrorist Ted Kaczynski, law enforcement sources told NBC News.

Kaczynski, whose bombs killed three people, long decried the ills of modern American life and harbored other antiestablishment views.

“We don’t think that there’s any specific threats to other people mentioned in that document,” NYPD Chief of Detectives Joseph Kenny said. “But it does seem that he has some ill will toward corporate America.”

Mangione also had a weapon that might have been homemade and thus off the radar of any law enforcement or government agency.

“The information we’re getting from Altoona is that the gun appears to be a ghost gun and may have been made on a 3D printer,” Kenny said.

“He was in possession of a ghost gun that had the capability of firing 9 mm round and a suppressor,” he said.

Police said the public’s help played a key role in making the arrest.

“There’s numerous linchpins in this case,” Kenny said. “We’ve recovered an enormous amount of forensic evidence, an enormous amount of video, and once again, with your help, the public’s help.”

Tisch said police found clothes matching the suspected gunman’s and a fake ID used at a New York City hostel.

The name on a fraudulent New Jersey driver’s license was for a 26-year-old Maplewood resident listed as “Mark Rosario,” according to an image of the phony ID obtained by NBC New York.

That name matches the one Thompson’s alleged killer used to check into a New York hostel days before the attack, multiple law enforcement sources told NBC News.

The man in custody had “multiple fraudulent IDs, as well as a U.S. passport,” Tisch said. But police don’t believe he was plotting an international escape.

Thompson was killed in front of the New York Hilton Midtown, about 280 miles from Altoona, by a masked assailant who approached from behind.

The shooter opened fire around 6:45 a.m., security video showed, before he ran away and then fled on a bike into Central Park, authorities said. The last video of the alleged gunman put him at a bus depot in upper Manhattan, police said.

Three pieces of ammunition were recovered with the words “deny,” “delay” and “depose” written on them in marker, one on each, police said.

The FBI has posted a $50,000 reward for information leading to the arrest of the gunman — in addition to the combined $10,000 offered by Crime Stoppers and New York police.

“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,” a UnitedHealthcare representative said Monday. “We thank law enforcement and will continue to work with them on this investigation.”

Thompson’s death sent shock waves throughout the corporate and health care worlds, raising questions about appropriate security for top-level executives.

The shooting also exposed a deep, ugly resentment against private health care companies as social media feeds were flooded with posts celebrating — or at least seeking to justify — Thompson’s slaying.

Thompson, who lived in Minnesota, had recently received threats but hadn’t altered his travel routine, said his wife, Paulette Thompson.

He wasn’t with a security detail when he was shot.

“Yes, there had been some threats,” Paulette Thompson said hours after the attack. “Basically, I don’t know, a lack of coverage? I don’t know details. I just know that he said there were some people that had been threatening him.”

Pennsylvania Gov. Josh Shapiro criticized online praise that followed Thompson’s slaying.

“Some attention in this case, especially online, has been deeply disturbing, as some have looked to celebrate instead of condemning this killer,” Shapiro said Monday evening at a news conference detailing the arrest and charges.

“Brian Thompson was a father to two. He was a husband, and he was a friend to many, and yes, he was the CEO of a health insurance company,” he said. “In America, we do not kill people in cold blood to resolve policy differences or express a viewpoint.”