As New York prosecutors worked Thursday to file murder charges against Luigi Mangione for the brazen killing of UnitedHealthcare CEO Brian Thompson, supporters of the suspect are donating tens of thousands of dollars to a defense fund set up for him, raising concerns among Mangione in law enforcement be made a martyr.

Several online defense funds have been set up for Mangione by anonymous people, including one on the crowdfunding website GiveSendGo that had raised over $50,000 as of Thursday afternoon.

The GiveSendGo defense fund for 26-year-old Mangione was founded by an anonymous group calling itself the “December 4th Judicial Committee,” apparently in reference to the day Mangione allegedly ambushed and shot Thompson in midtown Manhattan. when the manager went to the company’s shareholders’ conference at New York’s Hilton Hotel.

“We are not here to celebrate violence, but we believe in the constitutional right to fair legal representation,” the anonymous group said in a statement.

The crowdfunding campaign sparked donations from more than 1,500 anonymous donors across the country. Many of them left messages of support for Mangione, including one person who described himself as “a frustrated citizen” and thanked Mangione for “raising awareness and thoughts in this sleeping nation.” .”

The GiveSendGo fund for Mangione appeared to have been briefly dissolved before being restored on Thursday.

In a statement to ABC News, a spokesperson for GiveSendGo said the company “operates under the policy of not preemptively determining guilt or innocence.”

“Our platform does not decide legal matters or the validity of legal grounds. Instead, we allow campaigns to remain active unless they violate the specific terms set out in our Terms of Service. Importantly, we allow legal defense fund campaigns as we believe everyone deserves the opportunity to have access to due process,” the GiveSendGo spokesperson said.

The spokesperson added: “We understand the concerns such campaigns raise and take this matter seriously. When campaigns are reported, our team conducts a thorough review to ensure they comply with our policies. While other platforms may take a different approach, GiveSendGo’s core value is to create a space where all people, regardless of their situation, can seek and receive support, with donors able to make their own informed decisions. “

Other crowdfunding sites such as GoFundMe have also suspended fundraising campaigns for Mangione’s defense.

“GoFundMe’s terms of service prohibit fundraising for the legal defense of violent crimes,” the crowdfunding website said in a statement. “The fundraisers have been removed from our platform and all donors have been refunded.”

Amazon and Etsy have removed merchandise featuring Mangione from their websites, including T-shirts and tote bags with the words “Free Luigi” and the words “Deny, Defend, Depose” that police say were engraved on bullet casings discovered at the scene of Thompson’s killing .

“Celebrating this behavior is abhorrent to me. It is deeply disturbing,” Manhattan District Attorney Alvin Bragg said in an interview with ABC News senior investigative reporter Aaron Katersky on Wednesday evening. “And what I want to say to members of the public, to people who are celebrating this as you’ve described and perhaps thinking about other measures, is that we will be vigilant and we will hold people to account. We are ready.”

Prosecutors in the Manhattan district attorney’s office have begun presenting evidence to a grand jury as they seek to secure an indictment against Mangione, sources told ABC News on Thursday.

Mangione’s attorney, Thomas Dickey of Altoona, Pennsylvania, where the suspect was arrested Monday after a five-day manhunt, said his client is presumed innocent and will plead not guilty to all charges against him. Mangione is fighting extradition to New York.

Asked about people who have emerged donating to Mangione defense funds, Dickey said: “People are entitled to their opinion, and like I said, if you’re an American and you believe in the American criminal justice system, you have to condemn him.” “To be innocent and none of us would want anything different if we were in her shoes. That’s why I’m glad he had support.

In a later interview on CNN, Dickey said he tended not to accept money from his client’s supporters for his defense.

“To be honest, I probably wouldn’t do that,” Dickey told CNN. “I just don’t feel comfortable there. Well, I don’t know. I didn’t think about it that much. Obviously my client appreciates the support he has, but I don’t know, that’s just not the case. “That really doesn’t suit me.”

Retired FBI special agent Richard Frankel said suspects in previous politically motivated violent crimes had received unsolicited assistance.

“We saw it with the Unabomber,” said Frankel, an ABC News contributor, referring to Ted Kaczynski — the mathematician-turned-domestic-terrorist who blamed technology for the decline in individual freedom and who died between 1978 and In 1995, hand-made explosives were sent to targeted individuals.

Frankel said Eric Rudolph, who detonated a bomb at Atlanta’s Centennial Olympic Park during the 1996 Olympics and carried out three other bombings while evading capture for five years, also found followers.

“In my opinion, they are supporting individuals who have committed potentially terrorist acts, but it is a politically charged act,” Frankel said

Referring to Thompson’s murder, Frankel added: “You can get upset about the health care industry, but you can’t threaten or actually harm members of the health care industry.”

Most recently, Marine veteran Daniel Penny was acquitted of the manslaughter of Jordan Neely, a homeless man who behaved erratically on a New York subway in a chokehold, after supporters donated more than $3 million to his legal defense fund.

Police officials have expressed concern that Mangione is being made a martyr. Someone posted wanted posters outside the New York Stock Exchange this week naming other executives.

A bulletin released Wednesday by the Delaware Valley Intelligence Center, a Philadelphia-based interagency law enforcement information sharing network, showed a photo of a banner hanging from an overpass that read “Deny, Defend, Deny.”

“Many social media users have openly spoken out in support of the continued assassination of CEOs, with some aiming to spread fear by publishing ‘hit lists,'” said the bulletin, obtained by ABC News.

Meanwhile, New York Police Department investigators continue to build a murder case against Mangione, who is being held in Pennsylvania on charges stemming from his arrest there, including illegal possession of a ghost gun and fraudulent identification. Mangione pleaded not guilty in Pennsylvania.

On Wednesday, New York Police Commissioner Jessica Tisch said the three shell casings found at the scene of Thompson’s shooting matched the gun Mangione found when he was arrested. She also confirmed that Mangione’s fingerprints were found on a water bottle and granola bar packaging found near the crime scene.