The suspect accused of killing UnitedHealthCare CEO Brian Thompson has pleaded not guilty to murder and terrorism charges in New York state.
Luigi Mangione, 26, appeared in court Monday to be arraigned on 11 state charges, including murder as a terroristic offense.
He also faces federal charges of stalking and murder, which could carry the death penalty.
Prosecutors say Mr. Mangione shot Mr. Thompson in midtown Manhattan before fleeing. Authorities later arrested him at a McDonald's in Pennsylvania.
Mr. Mangione appeared in court on Monday wearing a maroon sweater, white collared shirt and khaki pants.
In addition to the long stream of journalists waiting for the suspect to appear, members of the public – almost all young women – were in court, some of whom told CBS, the BBC's American partner, that they were there to show their support.
Mr. Mangione faces 11 charges in New York state, including first-degree murder and murder as a crime of terrorism.
If convicted on all counts, he faces a mandatory sentence of life in prison without the possibility of parole.
Federal prosecutors also separately charged Mr. Mangione with using a firearm to commit murder and an interstate pursuit resulting in death. Both charges could make him eligible for the death penalty.
He has not yet entered a plea on those charges.
Prosecutors said the federal and state cases will run parallel to each other.
In court last week, Mr. Mangione's lawyer – Karen Friedman Agnifilo – said the two sets of charges appeared to contradict each other, with the state charges accusing him of trying to “intimidate or coerce a civilian population” while the federal charges focused on crimes against an individual. .
Ms Anifilo said the overlapping cases were “confusing” and “very unusual”.
“I've never seen anything like what's going on here” in 30 years of practicing law, she said.
In court on Monday, she also told the judge that she felt statements by government officials – including New York City Mayor Eric Adams – made her “very concerned about my client's right to a fair trial.”
“It's a young man,” she said. “He's being treated here like a human ping-pong ball between warring jurisdictions.”
Judge Gregory Caro said he was unable to control what happened outside the court, but promised that Mr. Mangione would receive a fair trial.
The suspect is currently in federal custody at the Metropolitan Detention Center (MDC) Brooklyn after being returned to New York under heightened security last week.
The authorities believe that Mr. Mangione carried out the targeted killing of Mr. Thompson, pointing to evidence that he was angry at the American health care industry.
The federal complaint noted that a notebook found in Mr. Mangione's possession expressed “hostility toward the health insurance industry, and particularly toward wealthy executives.”
Some on social media praised Mr. Mangione's alleged crimes, often sharing their own anger at the US private health care system.
Speaking to CBS, the BBC's US affiliate, on Sunday, Homeland Security Secretary Alejandro Mayorkas said the online rhetoric was “extremely worrying”.
“It speaks to what's really boiling over here in this country,” he said. “And unfortunately we're seeing that play out in the violence, the domestic violent extremism that exists.”