Former NYPD inspector 'skeptical' UnitedHealthcare CEO gunman was professional, zeroes in on weapon of choice

Former NYPD inspector and Fox News Contributor Paul Mauro said the type of weapon used by the gunman who murdered UnitedHealthcare CEO Brian Thompson outside a Midtown Manhattan Hilton hotel Wednesday could work to police's advantage, and addressed rumors the suspect may have worked as a hitman.

"The speculation is that it's a hit man, it's a professional killer and all this sort of stuff…I would just hesitate on that and tell people to just be mindful of the fact that professional hitmen primarily exist in the movies. They don't really exist," Mauro told Fox News Digital. Mauro says everything we know at this point is just speculation.

In video obtained by Fox News Digital, Thompson is seen walking down a sidewalk outside the Hilton Hotel in Midtown Manhattan early Wednesday morning when a masked man guns him down before fleeing the scene.

"What we know so far is that he was very calm, he clearly knew the route…it doesn't mean it wasn't a murder for hire. Those things do happen. The idea that this is a ‘professional shooter’ I am skeptical of," Mauro said.

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Mauro said what makes this case even more interesting is the type of gun that was used.

"Now he looks like he's got either a very long barrel or a silencer. Silencers are de facto illegal, and they're very, very hard to come by. So a lot of them are homemade. That said, it could just be a long barrel gun," Mauro described. 

"The gun appears to need to be racked after each shot. Unusual." 

He added that there are guns like that, and they're designed to suppress the sound, but that there are also add-on features that can be added to keep the slide of a semiautomatic gun from wrecking.

"That means that after you shoot, you're going to have to rack the slide of the gun in order to shoot again. He does that in the video, which argues that he may have added, and he may have modified the gun because these are sort of after market things that you can add to the gun," Mauro said.

"So what I would say is, is somebody with a familiarity with guns and, particularly, this gun looks to be a rare type of gun. And that's a data point that the police can chase down."

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Firearms expert David Katz, a former DEA firearms instructor who is now the CEO of Global Security Inc., agreed that the suspect was not a professional, but may have been using a rare pistol. 

Katz told Fox News Digital that he believes the weapon may have been a bolt action pistol, a "modernized version of a World War II pistol."

"The operation that he does with his hands is consistent with the operation of that weapon," he said, noting that he "immediately moved to rack the slide manually with his left hand" after he fired. 

"He knew he had to chamber around every time he fired a shot," he said. Katz said the suspect was "not a master spy" and he "made a lot of stupid mistakes.

"And if it is that pistol, it is a very unique pistol and they don’t make that many of them,"he noted, adding, "If it is that gun they will be able to narrow him down to a very small number of purchasers." 

Multiple law enforcement contacts told Fox News that they believed the weapon used in the murder resembled a "Welrod", a bolt action, suppressed pistol first used in WW2.

"I’d bet my pension that this is the weapon that was used on the United CEO. It’s very, very quiet and requires manual cycling after each round is fired. Top choice by pros for up-close, quiet work," the source told Fox News. 

Forensic pathologist Dr. Michael Baden also told Fox News Digital the first item in terms of forensic pathology is determining whether the bullets passed through.

"If the bullets are in and out, they've got to really look for the bullets at the scene, and not wait until after the autopsy," Baden said. 

Baden said this was crucial for investigators to do because the streets could be cleaned by then so that could prohibit them from finding where the bullets went and their path.

He added that Thompson probably died so quickly because his lungs were injured, but that investigators will know more in the next 24-48 hours.

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"They'll know how many shots were fired, whether any went in and out, they'll recover the bullets and get more information, in addition to what they already have on the shell casings," Baden said. "The unshot bullets are interesting, but irrelevant as far as saying that it came from his gun -- if they find the gun."

The Hilton Hotel was hosting the UnitedHealthcare annual investors meeting, and police said Thompson had been in town from Minnesota since Monday and was staying across the street. 

Mauro believes since Thompson had been there since Monday, the shooter would have had other opportunities to go after Thompson, but the convention seems to be the jumping off point. 

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New York City Crimestoppers is offering a combined reward of up to $10,000 for information leading to an arrest and indictment.

Anyone with information is encouraged to contact Crime Stoppers at 1-800-577-TIPS, or for Spanish, 1-888-57-PISTA. Tips can also be submitted on the Crime Stoppers website by visiting crimestoppers.nypdonline.com.

Fox News' Michael Ruiz, Danielle Wallace, Greg Wehner, and Bill Melugin contributed to this report. 

Stepheny Price is writer for Fox News Digital and Fox Business. Story tips and ideas can be sent to stepheny.price@fox.com