Lead Mangione detective says silencer found in case was unlike anything he'd seen in 25 years
A retired NYPD detective who investigated the assassination of UnitedHealthcare CEO Brian Thompson said in a new interview that the silencer recovered is unlike anything he had previously encountered, underscoring what investigators say was the sophistication and planning behind the slaying.
Retired NYPD Detective Sgt. John Griffin told "Dateline" Friday that in 25 years on the job, he'd never seen one before.
"It had something on the front, like a homemade suppressor or silencer-type thing," said the detective, who was part of the NYPD's major crimes unit.
Luigi Mangione, 28, is accused of assassinating Thompson, a 50-year-old father of two from Minnesota who was gunned down on video outside a Manhattan Hilton hotel on the morning of a planned investor conference on Dec. 4, 2024.
Pat Diaz, a private investigator who spent 30 years as a homicide detective in the Miami area, told Fox News Digital Monday that silencers were a big part of the violent "Cocaine Cowboys" and mafia era of the 1980s and 1990s.
"Usually on major drug killings, they'd just drop the weapon there, because most of the time they were untraceable," he said. "It wasn't unusual in the '80s, '90s, to come up with a firearm with a silencer on it — especially in Miami."
Stricter laws diminished their use in more recent decades, but they are making a resurgence, he said.
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The 3D-printed version shows some capability with mechanical engineering as well as intent, he added.
"It shows his frame of mind," Diaz said. "Insanity is out the door, because he was of sound mind to be able to engineer and design a silencer."
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Typically, a printed device requires multiple components to be created and then assembled — then fitted to the weapon safely.
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The former Ivy Leaguer has pleaded not guilty to state and federal charges in connection with the case and could face life in prison without parole if convicted on the most serious federal charges.
In New York, he faces a maximum penalty of life imprisonment if convicted, which would include a chance of parole.
"In 25 years, I don't think I've ever actually encountered a silencer before that," Griffin told "Dateline."
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Surveillance video shows a hooded man approach Thompson from behind and open fire with a handgun.
NYPD detectives were able to trace the suspect's movements back from the crime scene to a hostel where they found surveillance video where he pulled his mask down and smiled at the clerk.
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That image circulated widely, leading customers and workers at a Pennsylvania McDonald's to call 911 five days later when Mangione was eating breakfast at a corner table.
He was arrested there, and searches of his bag allegedly turned up the suspected murder weapon and a 3D-printed suppressor.
"You go back to the theory that these guys think they can get away with anything," Diaz said. "Somebody recognized him...In New York he's one among millions — where he went, he stood out as an outsider."
Mangione is due back in both courthouses next week.