UnitedHealthcare CEO murder: What you need to know about the ghost gun allegedly carried by Luigi Mangione

as Luigi Mangione He was handcuffed and taken into custody Monday in Pennsylvania, where police searched a backpack he was carrying and found what they described as a loaded 3D-printed firearm, a silencer and one loose bullet.

“Officers located a black 3D printed handgun and a black silencer,” wrote Tyler Frye and Joseph Detwiler of the Altoona Police Department in a criminal complaint. They described the weapon as having a “metal bolt and plastic grip with a metal rifled barrel.”

“The gun had one loaded Glock magazine with six 9mm full metal cased rounds. There was also one loose nine-millimeter hollow-point cartridge,” the officers wrote. “The muffler was also 3D printed.”

NYPD chiefs on investigation and arrest in murder of UnitedHealthcare CEO

Mangione, who New York officials charged with second-degree murder in connection with last week’s “insolence” assassination of the CEO in Manhattan, was first arrested in Altoona on Monday on charges that included a felony involving a gun, according to a criminal complaint.

Mangione was charged with a third-degree felony for allegedly carrying a concealed firearm without a license, according to the complaint. He was also charged with a felony for allegedly “possessing the tools of a crime,” along with three additional charges in Pennsylvania related to allegedly lying to police about his identity.

New York Police Chief Joseph Kenney said Monday that the weapon would undergo ballistics testing. He said information about the gun began coming in from Altoona police and that it appeared to be a “ghost gun,” meaning it had no serial number and could not be traced.

“It may have been 3D-printed with the ability to fire a 9mm round,” Kenney said. “Obviously, that will become known during our ballistics testing.”

Kenney said it is too early in the investigation to determine whether the gun may have been made by the suspect or purchased. But the gun and 3D-printed silencer were “consistent with the weapon used in the murder,” NYPD Commissioner Jessica Tisch said after Mangione’s arrest Monday.

Last week, law enforcement officials scrutinized what kind of weapon might have been used in the killing, officials said, because the gun was somewhat unique in its operation.

Kenney said last week that detectives had reviewed the surveillance video that showed the fatal shooting, saying it appeared to show “that the gun is malfunctioning when it clears the jam and starts firing again.”

Police sources told ABC News on Thursday that these apparent malfunctions could indicate that the weapon is B&T Station Six, a type of pistol with a built-in silencer, known in the UK as the Welrod pistol.

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Such firearms have long barrels that allow them to fire 9mm bullets almost silently, officials say. They also require you to manually cycle cartridges from the magazine.

But New York City Mayor Eric Adams said untraceable guns were “extremely dangerous,” adding that federal legislation was needed to “suppress the availability of ghost guns.”

ABC New’s Aaron Katerski, Peter Haralambous, Mark Krudele and Josh Margolin contributed to this report.