The brazen assassination outside of a hotel in Manhattan last week sparked a nationwide manhunt that came to an end in the Pennsylvania town.
Luigi Mangione, 26, was arrested on Monday at the McDonald's. He is facing several charges, including for Thompson's murder.
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One man who visits the Altoona McDonald's regularly told Action News he was there on Monday at the same time as Mangione. He said many people, including the worker, seemed to be aware of the manhunt and were wondering if the suspicious-looking man was the wanted suspect.
Eventually, that McDonald's workers called the police.
Shockwaves continue to roll through Altoona at the McDonald's where Mangione was arrested Monday.
"From what I was told, the worker that took his orders she said his eyes and his eyebrows -- she just thought it was him," said Larry, who did not provide his last name. "I think she approached two of the managers and said, 'I think the shooter from New York's in here.'"
Larry said he didn't report it but a friend thought he recognized Mangione too.
"We pretty much laughed about it like, 'Oh yeah, sure. Ok.' But it turned out it was him," Larry recalled.
Authorities in New York have charged Mangione with the murder of United Healthcare CEO Brian Thompson in midtown Manhattan last week.
He also faces charges in Pennsylvania for lying to police about his identity and possession of a gun without a license, which police say was a 3D-printed gun and silencer.
"We say this all the time, if you see something, say something. Do something, and this case that McDonald's employee did just that, and we are grateful as the city to that person," said NYPD Commissioner Jessica Tisch.
As officials heap praise on the unidentified McDonalds worker, they're doing the same for the Altoona Police Officer Taylor Frye, who made the arrest.
Frye has only been on the job for six months. He spoke briefly on Monday night at the Blair County courthouse about this high point in his short career.
"I can't say I was expecting it by any means but it feels good to get a guy like that off the street, especially starting my career this way it feels great," Frye said.
Meanwhile, investigators are still asking for tips while they continue to piece together a timeline of Mangione's movements from New York and across Pennsylvania.
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"I still can't hardly believe it's for real," Larry said.
Mangione needs to be back in court in Blair County on December 23.
He is currently housed at SCI Huntington.
There has been no word on when he'll be extradited back to New York City to face murder charges.