Luigi Mangione, suspect in the murder of the UnitedHealthcare CEO, has hired high-profile defense attorney Karen Friedman Agnifilo, a former prosecutor with the Manhattan district attorney's office.

Mangione retained the services of Manhattan defense attorney Karen Friedman, a longtime veteran of the Manhattan District Attorney’s Office.

Supporters of Luigi Mangione are raising tens of thousands of dollars for his defense fund.

Luigi Mangione's mother filed a missing persons report about her son in San Francisco 16 days before he allegedly shot dead UnitedHealthcare CEO Brian Thompson.

Luigi Mangione -- the alleged killer of UnitedHealthcare CEO Brian Thompson -- has been greeted by a surge of enthusiastic online support.

Mangione’s mother had filed a missing persons report about her son on Nov. 18.

Luigi Mangione may waive extradition from Pennsylvania to New York City to face murder charges for killing of UnitedHealthcare CEO Brian Thompson, according to Manhattan District Attorney Alvin Bragg.

Luigi Mangione may waive extradition to New York City as early as Tuesday, Manhattan District Attorney Alvin Bragg said on Friday.

The day after a masked gunman killed the CEO of UnitedHealthcare in New York City, police in San Francisco gave the FBI a potentially valuable tip about the identity of the suspect

Luigi Mangione has been charged with second-degree murder in the killing of UnitedHealthcare CEO Brian Thompson.

The man charged with murder for gunning down UnitedHealthcare CEO Brian Thompson was arrested and charged after the shooting outside a Hilton Hotel in Midtown Manhattan.

ABC News’ Aaron Katersky reports on the probe into Luigi Mangione, the suspect accused of killing UnitedHealthcare CEO Brian Thompson, who is fighting extradition.

Sources tell ABC News that prosecutors have started presenting evidence against Mangione to a grand jury, seeking an indictment that could strengthen their case for his extradition from Pennsylvania.

In Pennsylvania, Luigi Mangione faces charges for allegedly possessing an untraceable ghost gun. In New York, he is charged with second-degree murder.

The firearm found on the suspect in the murder of the UnitedHealthcare CEO is believed to have been an untraceable ghost gun, according to police.

Police investigators say they have matched the gun to three shell casings found at the scene and matched Luigi Mangione’s fingerprints to prints found near where Brian Thompson was gunned down.

ABC News’ Aaron Katersky discusses the legal moves as Manhattan prosecutors work to secure an indictment against Luigi Mangione for the killing of UnitedHealthcare CEO Brian Thompson.

The ghost gun allegedly in Luigi Mangione's possession when he was arrested has been matched to three shell casings recovered at the crime scene in New York.

"Wanted" signs naming executives were posted in Manhattan this week, NYPD said.

Luigi Mangione was charged in Pennsylvania with carrying a gun without a license, forgery, falsely identifying himself to police and possessing "instruments of crime."

The suspect charged in the fatal shooting of UnitedHealthcare CEO Brian Thompson was arrested in Altoona, Pennsylvania.

Luigi Mangione, who is accused of killing Brian Thompson in New York, could face additional charges, according to Manhattan District Attorney Alvin Bragg.

Luigi Mangione was found in possession of a ghost gun that matches three shell casings recovered at the site of Brian Thompson’s fatal shooting in Midtown Manhattan, according to the NYPD.

The murder of UnitedHealthcare CEO Brian Thompson, combined with the alleged grievances of the man suspected of shooting him, have put health care in the spotlight.

ABC News’ Linsey Davis spoke to Luigi Mangione’s former classmate, Hari Menon, who describes the suspect in the killing of UnitedHealthcare CEO Brian Thompson as a “super nice upperclassman.”

Plus, the latest on President-elect's transition and cabinet picks as well as a look at the debut of Kylie Kelce's podcast.

A week after UnitedHealthcare CEO Brian Thompson was shot and killed in New York, the health insurer's parent company is praising him as "one of the good guys."

Luigi Mangione was taken into custody in Pennsylvania on Monday following a dayslong manhunt for the suspect in the fatal shooting of UnitedHealthcare CEO Brian Thompson.

Luigi Mangione is charged with murder in the Dec. 4 fatal shooting of UnitedHealthcare CEO Brian Thompson.

Luigi Mangione, 26, is accused of killing UnitedHealthcare CEO Brian Thompson.

The ghost gun allegedly in Luigi Mangione's possession in Pennsylvania was matched to three shell chasings recovered in New York, according to police commissioner Jessica Tisch.

Luigi Mangione refused to waive extradition from Pennsylvania to New York where he is charged with murdering UnitedHealthcare CEO Brian Thompson.

Thomas Dickey, the defense attorney for Mangione, who is accused of killing Brian Thompson, discusses his client’s refusal to waive extradition to New York and concerns over evidence in the case.

Luigi Mangione appeared to frequently discuss what he claimed were his health troubles -- including back pain, brain fog, and sciatica -- online.

Before he was arrested Luigi Mangione walked into the Horseshoe Curve Lodge in Altoona, Pennsylvania, one morning looking for a room, according to the desk clerk.

Luigi Mangione appeared to frequently discuss what he claimed were his health troubles -- including back pain, brain fog, and sciatica -- online.

Luigi Mangione yelled to the press about "an insult to the intelligence of the American people" as he was physically dragged into a Pennsylvania courthouse.

The bulletin warned that Thompson's killing may be used as "messaging and propaganda" to share the techniques and tactics for targeting other health care companies.

Online posts have listed the names and salaries of health insurance executives and "Wanted" signs have been posted in Manhattan, according to the bulletin.

Luigi Mangione may have found inspiration in Ted Kaczynski, police intel says.

The suspect in the shooting of the United Healthcare CEO had several handwritten pages on him that indicated frustration with the health care system, a detective said.

UnitedHealthcare CEO shooting suspect Luigi Mangione has arrived at his extradition hearing, shouting at gathered press outside of the Pennsylvania courtroom.

White House press secretary Karine Jean-Pierre addressed the UnitedHealthcare CEO shooting and sent condolences to the victim's family.

Former FBI agent Brad Garrett discusses the investigation into Luigi Mangione, the suspect arrested in connection to the shooting of UnitedHealthcare CEO Brian Thompson.

Mangione is a May 2020 graduate of the University of Pennsylvania, according to a school spokesperson. He earned bachelor's and master's degrees in engineering from the Ivy League institution.

Jessica Tisch and Joseph Kenney join "GMA" to discuss the investigation and charges facing suspect Luigi Mangione in the shooting of UnitedHealthcare CEO Brian Thompson.

Luigi Mangione was arrested at a McDonald’s in Pennsylvania, after he was recognized from surveillance images, and is facing a second-degree murder charge in New York in the death of Brian Thompson.

The NYPD filed second-degree murder charges against Luigi Mangione, the suspected shooter of UnitedHealthcare CEO Brian Thompson, according to an online court docket.

Luigi Mangione was arrested by Pennsylvania police on unrelated charges, authorities said. The 26-year-old is in custody as a suspect in connection with Brian Thompson's murder.

Luigi Mangione is in custody in Altoona, Pennsylvania, as a person of interest in the murder of UnitedHealthcare CEO Brian Thompson in New York City last week, according to authorities.