US prosecutors will seek the death penalty for Luigi Mangione, the man accused of shooting dead UnitedHealthcare CEO Brian Thompson in December.

Attorney General Pam Bondi said in a statement on Tuesday that she had directed federal prosecutors to seek capital punishment for the “premeditated, cold-blooded assassination”.

Mr Thompson was shot dead outside a hotel in New York on 4 December. Police arrested Mr Mangione, 26, days later in Pennsylvania after a nationwide manhunt.

He has pleaded not guilty to state charges, and has yet to enter a plea for separate federal charges. He is awaiting trial in a New York prison.

In the press release, Bondi said Mr Thompson’s murder “was an act of political violence” and that it “may have posed grave risk of death to additional persons” nearby.

Investigators say Mr Mangione was motivated to kill Mr Thompson, 50, because of anger with US health insurance companies.

A lawyer for Mr Mangione called the decision “barbaric”, accused the government of “defending the broken, immoral, and murderous healthcare industry”, and said Mr Mangione was caught in a tug-of-war between state and federal prosecutors.

“While claiming to protect against murder, the federal government moves to commit the pre-meditated, state-sponsored murder of Luigi,” said Karen Friedman Agnifilo in a statement.

Mr Mangione is facing 11 state criminal counts in New York, including first-degree murder and murder as a crime of terrorism.

If convicted of all the counts, he would face a mandatory sentence of life in prison without the possibility of parole.

But federal prosecutors have also separately charged Mr Mangione for using a firearm to commit murder and interstate stalking resulting in death. These charges make him eligible for the death penalty.

Prosecutors have said the federal and state cases will move forward parallel with one another.

Mr Mangione is being held at the Metropolitan Detention Center (MDC) Brooklyn.

New York prosecutors have already shared some evidence in their case against him, including a positive match of his fingerprints with those discovered at the crime scene.

According to New York District Attorney Alvin Bragg, Mr Mangione arrived in New York City on 24 November and stayed in a Manhattan hostel using a fake ID for 10 days before carrying out the attack against Mr Thompson.

The healthcare boss was shot in the back by a masked assailant on 4 December as he was walking into a hotel where the company he led was holding an investors’ meeting.

A nationwide search led police to Mr Mangione five days later at a McDonald’s hundreds of miles away in Altoona, Pennsylvania.

Police said that when they found Mr Mangione, he was in possession of a ghost gun – a firearm assembled from untraceable parts – a fake ID, a passport and a handwritten document indicating “motivation and mindset”.

Mr Thompson’s killing ignited a fraught debate about how the US healthcare system operates.

Some Americans, who pay more for healthcare than people in any other country, expressed anger over what they see as unfair treatment by insurance firms.

US Homeland Security Secretary Alejandro Mayorkas said in December that the rhetoric on social media in the wake of the killing was “extraordinarily alarming”.

“It speaks of what is really bubbling here in this country, and unfortunately we see that manifested in violence, the domestic violent extremism that exists,” he told CBS’s Face the Nation.