The man accused of fatally shooting the CEO of UnitedHealthcare pleaded not guilty on Monday to murder and terror charges in a state case that will run parallel to his federal prosecution.Luigi Mangione, 26, was shackled and seated in a Manhattan court when he leaned over to a microphone to enter his plea. The Manhattan district attorney formally charged him last week with multiple counts of murder, including murder as an act of terrorism.His initial appearance in New York's state's trial court was preempted by federal prosecutors bringing their own charges over the shooting. The federal charges could carry the possibility of the death penalty, while the maximum sentence for the state charges is life in prison without parole.Prosecutors have said the two cases will proceed on parallel tracks, with the state charges expected to go to trial first.Authorities say Mangione gunned down Brian Thompson as he was walking to an investor conference in midtown Manhattan on the morning of Dec 4.Mangione was arrested in a Pennsylvania McDonald's after a five-day search, carrying a gun that matched the one used in the shooting and a fake ID, police said. He also was carrying a notebook expressing hostility toward the health insurance industry and especially wealthy executives, according to federal prosecutors.At a news conference announcing the state charges last Tuesday, Manhattan DA Alvin Bragg said the application of the terrorism law reflected the severity of a "frightening, well-planned, targeted murder that was intended to cause shock and attention and intimidation.""In its most basic terms, this was a killing that was intended to evoke terror," he added. "And we've seen that reaction."Karen Friedman Agnifilo, an attorney for Mangione, has accused federal and state prosecutors of advancing conflicting legal theories. In federal court last week, she called their approach "very confusing" and "highly unusual."Mangione is being held in a Brooklyn federal jail alongside several other high-profile defendants, including Sean "Diddy" Combs and Sam Bankman-Fried.Mangione was extradited from Pennsylvania on Thursday and quickly rushed to New York City, where he was seen wearing an orange jumpsuit as he was led away from a helicopter by heavily armed police officers and New York City Mayor Eric Adams.Adams said he was hoping to send a message to the suspect: "I wanted to look him in the eye and say you carried out this terroristic act in my city — the city that the people of New York love," the mayor told a local TV station. "I wanted to be there to show the symbolism of that."An Ivy-league graduate from a prominent Maryland family, Mangione appeared to have cut himself off from family and friends in recent months. He posted frequently in online forums about his struggles with back pain. He was never a UnitedHealthcare client, according to the insurer.Thompson, a married father of two high-schoolers, had worked at the giant UnitedHealth Group for 20 years and became CEO of its insurance arm in 2021.The killing has prompted some to voice their resentment at U.S. health insurers, with Mangione serving as a stand-in for frustrations over coverage denials and hefty medical bills. It also has sent shockwaves through the corporate world, rattling executives who say they have received a spike in threats.