The GiveSendGo defense fund for the 26-year-old Mangione was established by an anonymous group calling itself "The December 4th Legal Committee," apparently in reference to the day Mangione allegedly ambushed and gunned down Thompson in Midtown Manhattan as the executive walked to his company's shareholders conference at the New York Hilton hotel.

Police say the evidence against Luigi Mangione includes fingerprints and notebook entries linking him to the shooting death of UnitedHealthcare CEO Brian Thompson.