The man charged in the murder of 50-year-old Brian Thompson, the CEO of Minnesota-based UnitedHealthcare who was fatally shot outside of a hotel in New York City a week ago, is fighting efforts to move him from Pennsylvania to New York to stand trial.

As of Wednesday morning, Luigi Mangione was being held without bail in Pennsylvania.

A few hours later, New York Police Department (NYPD) officials announced that the gun found on Mangione matched the shell casings found at the shooting scene.

In addition, NYPD Commissioner Jessica Tisch said Mangione’s fingerprints also matched a water bottle and a protein bar wrapper that police found near the scene, and that officials say the gunman bought them at a nearby coffee shop while waiting for Thompson.

Thomas Dickey, Mangione’s defense attorney, said early Wednesday morning that the reason they were fighting extradition to New York is because they had yet to see any of the actual evidence against Mangione. The evidence includes writings, fake IDs and a gun — Dickey said Wednesday morning that so far there is no evidence that links that particular firearm to the murder.

“I mean, a lot of guns look the same! That’s why they do ballistics, an examination, a test of all that to try and match that. Trust me, they’re going to try and match that firearm to the incident by more than just, ‘Well, it looks like that,'” said Dickey.

Dickey says he hopes to get his hands on all of the items found in his client’s backpack on Wednesday so he can examine them for himself.

As for the criminal charges out of New York, Mangione plans to plead not guilty to all counts filed against him when he eventually makes his first appearance in court, which is expected to happen later this month.

This all comes as a new warning is issued about threats to other executives in the insurance industry. Those threats to executives come in the form of a “hit list” that’s making rounds online, showing both the names and salaries of eight top executives.

A new bulletin from the New York Police Department (NYPD) tells CEOs they should all act like they have targets on their backs, as the “wanted” posters are now hung up near Wall Street, showing the names and faces of some of those corporate executives.

This now has police worried about the potential for copycat gunmen.

CLICK HERE for additional coverage from 5 EYEWITNESS NEWS on the shooting.

ABC News and the Associated Press contributed to this story.