NEW YORK -- Fingerprints recovered from items found near the shooting scene in Manhattan appear to match fingerprints taken from Luigi Mangione in Pennsylvania, police said. NYPD also said Wednesday the gun in his possession matches shell casings found on the scene.
The prints recovered from a water bottle and a cell phone were smudged, as ABC News has previously reported, but sources said they appear to match the prints sent from Altoona, where Mangione was arrested.
The ghost gun allegedly in Mangione's possession in Pennsylvania was matched to three shell chasings recovered in Midtown, New York City Police Commissioner Jessica Tisch said Wednesday.
She also confirmed fingerprints recovered in NYC have been matched to Mangione's in Pennsylvania
"First, we got the gun in question back from Pennsylvania. It's now in the NYPD crime lab. We were able to match that gun to the three shell casings that we found in Midtown at the scene of the homicide. We were also able in our crime lab to match the person of interest's fingerprints with fingerprints that we found, both on the water bottle, and the KIND bar near the scene of the homicide in midtown," Tisch said
Her remarks came in during an unrelated event with Mayor Eric Adams.
Writings were also recovered from Mangione in a spiral notebook, including plans concocting how to eventually kill the UnitedHealthcare CEO, according to law enforcement officials.
"What do you do? You whack the CEO at the annual parasitic bean-counter convention," one passage allegedly said.
The notebook also makes reference to the Unabomber, but the writings also said that using explosives could "risk innocents," according to the officials.
Detectives are still examining Mangione's writings but are considering the contents of the notebook to represent a confession, sources say.
Pennsylvania investigators have also started interviewing members of Mangione's family.
The defense attorney representing Mangione earlier on Wednesday told "Good Morning America" he has seen "no evidence" linking his client to the killing.
"Today's another day," attorney Thomas Dickey said. "We're looking forward to beginning our inquiry as to what evidence may or may not be out there."
The attorney said Mangione is "taking it as well as he can."
WATCH: Luigi Mangione's defense attorney speaks out
Mangione, 26, plans to challenge his extradition from Pennsylvania to New York, where he faces a charge of second-degree murder in connection with Brian Thompson's shooting death Dec. 4 outside a Midtown Manhattan hotel.
The Ivy League graduate was arrested on Monday in Altoona, Pennsylvania, and charged in Pennsylvania for allegedly possessing an untraceable "ghost" gun."
"He has constitutional rights and that's what he's doing" in challenging the interstate transfer, Dickey told reporters on Tuesday.
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He also cautioned that anyone speculating on the case should take the potential evidence "in its entirety," not taking pieces of writing or other evidence "out of context."
"People put out certain things, parts of different things," he said. "I think any lawyer involved in this situation would want to see it all."
Mangione plans to plead not guilty to the charges filed against him in Pennsylvania, Dickey said. A judge in Pennsylvania ordered Mangione held without bail on Tuesday.
The Manhattan District Attorney's Office said it will seek a governor's warrant to try to force Mangione's extradition. New York Gov. Kathy Hochul said in a statement that she'll sign a request for the governor's warrant "to ensure this individual is tried and held accountable."
Dickey said he anticipates that Mangione would also plead not guilty to the second-degree murder charge in New York.
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Mangione yelled to the press about "an insult to the intelligence of the American people" as he was physically dragged into the courthouse on Tuesday.
When Mangione was arrested on Monday, he had "written admissions about the crime" with him, according to the New York arrest warrant.
Mangione's writings, obtained by ABC News, were addressed to the "Feds" and said, "I do apologize for any strife of traumas but it had to be done. Frankly, these parasites simply had it coming."
He claimed that the U.S. has the most expensive health care system in the world, but ranks about No. 42 in life expectancy. He said UnitedHealthcare "has grown and grown, but as our life expectancy? No the reality is, these [indecipherable] have simply gotten too powerful, and they continue to abuse our country for immense profit."
Whether Mangione has a personal connection to UnitedHealthcare is unknown, NYPD Commissioner Jessica Tisch said.
A UnitedHealth Group spokesperson said in a statement that they hope the arrest "brings some relief to Brian's family, friends, colleagues and the many others affected by this unspeakable tragedy. We thank law enforcement and will continue to work with them on this investigation."
CNN Wire contributed to this report
ABC News' Peter Charalambous and Josh Margolin contributed to this report.