One of the Pennsylvania police officers who arrested accused assassin Luigi Mangione at a McDonald’s in Altoona last year took the witness stand in his evidence suppression hearing Tuesday morning, testifying about the moment he realized the suspicious person eating breakfast in a corner might be a suspected killer.

Altoona Police Officer Joseph Detwiler testified that while on his way to responding to the call, he didn’t expect to actually find the suspected assassin. But when he arrived, he said that as soon as Mangione pulled down his face mask he believed he was looking at a wanted man.

He testified that “within 2 seconds” he asked Mangione to pull his mask down, and then he was “100% sure” it was the man the NYPD was looking for.

“No doubt in my mind,” he testified.

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Detwiler said he never asked Mangione if he had murdered UnitedHealthcare CEO Brian Thompson. He testified that he asked for Mangione’s name, for his ID, if he had been to New York recently, where he was from and if he was from Altoona. 

He said he never said Mangione was under arrest, never prevented Mangione from leaving and never mentioned the shooting in New York City.

He said he grew suspicious and moved Mangione’s bag away from him, fearing there might be a weapon inside.

Later, police alleged they found the suspected murder weapon in the bag.

Under cross-examination, Detwiler testified that he did not obtain a search warrant before officers looked into Mangione’s bag. 

While authorities were placing Mangione under arrest, Detwiler testified that his superiors contacted the NYPD, Blair County District Attorney’s Office and potentially the FBI to alert them of the capture. 

When asked by Mangione’s defense team if Detwiler was proud of making the arrest, the officer testified that it was like any other case. However, the defense pressed Detwiler about a social media post depicting Detwiler receiving an award for Mangione’s arrest, in which Detwiler denied ever posting an image, instead telling the courtroom, “I didn’t. My wife did.” 

The suppression hearings will resume on Thursday. The judge ruled Tuesday that all exhibits used in these hearings will stay sealed until the trial begins.

Mangione is accused of shooting Thompson from behind outside a Manhattan hotel last year.

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Police grabbed journals and other writing from Mangione’s backpack. They also took his fake New Jersey ID, under the name “Mark Rosario,” and recovered the alleged murder weapon and a 3D-printed silencer.

Mangione’s defense has argued that the search of his belongings without a warrant was unlawful, and therefore the evidence should be suppressed. Prosecutors countered that police were doing their job within the bounds of the law and that the search was justified without requiring a warrant.

The defense also wants some of Mangione’s statements suppressed.

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First he allegedly gave police a fake name — the one that appears on his alleged fake ID from New Jersey, which police say he used to check into the Manhattan hostel days before Thompson’s assassination.

He also, while in custody, allegedly blurted out something about having a 3D-printed gun. The Pennsylvania jail guard who heard that statement testified that the accused assassin brought it up on his own.

Fox News Digital’s Julia Bonavita contributed to this report.