Luigi Mangione to Be Arraigned on New York State Charges on Monday

The 26-year-old man charged in the predawn killing of a health insurance executive on a Manhattan sidewalk this month is scheduled to make his first appearance in New York State Supreme Court on Monday, prosecutors said.

The man, Luigi Mangione, is facing three state murder charges, including two terrorism counts in the death of the executive, Brian Thompson. Mr. Mangione also faces weapons charges.

The hearing on Monday will be the first opportunity that Mr. Mangione and his lawyer, Karen Friedman Agnifilo, will have to formally respond to accusations leveled by the Manhattan district attorney’s office.

In addition, in a parallel case, federal prosecutors in Manhattan unsealed murder charges against Mr. Mangione on Thursday. He has pleaded not guilty to those charges.

The killing, in the early hours of Dec. 4, gave rise to a debate about the frustrations that Americans have with the health insurance industry — the high costs, the denials of coverage and what many say is the industry’s prioritization of profits.

Mr. Thompson, the chief executive of UnitedHealthcare, was walking that morning toward the entrance of a Hilton hotel on West 54th Street when a masked and hooded gunman opened fire behind him. Mr. Thompson, who was headed for an investor meeting, was shot once in the back and once in the leg.

Authorities have said that it was Mr. Mangione who waited nearly an hour outside the hotel that morning, armed with a 3-D-printed 9-millimeter handgun fitted with a suppressor. And as Mr. Thompson walked by, Mr. Mangione raised the weapon and fired, the police said.

Days later, Mr. Mangione was eating hash browns at a McDonald’s in Altoona, Pa., when a fellow customer remarked to a friend that he resembled a person in photos released by the New York Police Department. An employee, who overheard the conversation, alerted the local police and Mr. Mangione was arrested.

Officers found a handgun, ammunition and fake identification cards on him, as well as a 262-word handwritten manifesto in which he appeared to take responsibility for the killing.

Prosecutors in Manhattan, led by District Attorney Alvin L. Bragg, have said that Mr. Mangione meant to terrorize civilians.

“This was a frightening, well-planned, targeted murder that was intended to cause shock and attention and intimidation,” Mr. Bragg said at a news conference.

Ms. Friedman Agnifilo, Mr. Mangione’s lawyer, has called the parallel prosecutions a confusing and “highly unusual situation.” In federal court on Thursday, she voiced her frustration, saying that she had been prepared to defend her client that day in state proceedings.