Suspected UnitedHealthcare CEO assassin Luigi Mangione is due in court today as the NYPD is warning that business leaders and political figures may be at an increased risk less than a week after a sniper shot and killed Turning Point USA founder Charlie Kirk during a public event at Utah Valley University in Orem, Utah.

Mangione faces a slew of state and federal charges after police allege he stalked and ambushed Brian Thompson, the health insurer’s chief executive and a married father of two from Minnesota who was visiting New York City for an investor conference.

There are concerns that he has inspired copycats. He allegedly wrote messages on shell casings found at the scene. The suspected Kirk assassin also allegedly etched memes and anti-fascist rhetoric onto cartridges found in the alleged murder weapon.

Charlie Kirk hands out hats before speaking at Utah Valley University in Orem, Utah, Wednesday, Sept. 10, 2025, shortly before a sniper fatally shot him from a rooftop on the other side of the courtyard. (Tess Crowley/The Deseret News via AP)

Around Manhattan, increased security measures were visible Tuesday. At the Blackstone building, where a gunman burst in and killed four people in July, more than a dozen security guards were seen outside the front door.

Mangione, an Ivy League-educated scion of a wealthy Maryland family, has pleaded not guilty to nine state-level charges in New York, including murder as an act of terrorism.

Enhanced security visible at the Blackstone building on Park Avenue in Manhattan on Tuesday, Sept. 16, 2025. In July, a gunman stormed into the building and killed four people, injuring a fifth. (Fox News Digital)

He faces stalking and other charges at the federal level as well as firearms and forgery charges in Pennsylvania, where he was arrested.

Despite the allegations against him, he has received an alarming amount of support online, and supporters have been seen rallying outside his court appearances dressed up like the character Luigi from “Super Mario Bros.”

Supporters of Luigi Mangione gather outside of Manhattan Criminal Court for a hearing in the murder of UnitedHealth Care CEO Brian Thompson on September 16, 2025, in New York City. Mangione is accused of murdering UnitedHealthcare CEO Brian Thompson late last year. He is facing 11 counts for the December 4 shooting of Thompson outside a midtown Manhattan hotel, which set off a massive manhunt. He is also facing federal charges of murder and other charges in Pennsylvania, where he was arrested.  (Spencer Platt/Getty Images)

At an earlier hearing, court officers seized a note addressed to him written on heart-shaped paper, smuggled into the building in a pair of socks sent with civilian clothes he had been allowed to wear instead of a jailhouse jumpsuit. 

His attorneys arrived at Manhattan’s criminal courthouse a few minutes before his 9 a.m. hearing in front of Judge Gregory Carro.

Thompson, 50, spent 20 years working for UnitedHealth Group and became CEO of the UnitedHealthcare subsidiary in April 2021, according to his online bio. He had two children.