US Attorney-General Pam Bondi has instructed prosecutors to pursue the death penalty for Luigi Mangione, the man accused of murdering a health insurance boss in New York last year.
Her instructions follow President Donald Trump's pledge to bring back capital punishment after his predecessor, Joe Biden, put a moratorium on most federal executions.
"Luigi Mangione's murder of Brian Thompson — an innocent man and father of two young children — was a premeditated, cold-blooded assassination that shocked America," Ms Bondi said in a statement.
"After careful consideration, I have directed federal prosecutors to seek the death penalty in this case as we carry out President Trump's agenda to stop violent crime and Make America Safe Again."
Mr Mangione is accused of shooting Mr Thompson, the CEO of American insurance giant United Healthcare, outside a Manhattan hotel on December 4.
Federal prosecutors have charged Mr Mangione with murder using a firearm. They've described the killing as an act of political violence that put bystanders at risk.
Mr Mangione has pleaded not guilty to separate murder and terrorism charges in the state of New York. He is yet to enter a plea in the federal case, which is expected to be tried after the state case.
If he is convicted in the federal case, it would be up to the jury, not the judge, to decide whether to impose the death penalty.
Mr Mangione's lawyer, Karen Friedman Agnifilo, described the decision to seek the death penalty as "barbaric".
"While claiming to protect against murder, the federal government moves to commit the premeditated, state-sponsored murder of Luigi," she said.
'Restoring the death penalty'
In the US, the use of the death penalty is far more common in state cases than in federal cases.
Mr Biden had placed a moratorium on federal executions for all cases except terrorism and hate-motivated mass murder.
Late in his presidency, he commuted the sentences of 37 out of 40 prisoners on federal death row, ordering they instead serve life in prison without parole.
"I am more convinced than ever that we must stop the use of the death penalty at the federal level," he said at the time.
But Mr Trump made "restoring the death penalty" an early priority upon his return to the White House.
In January, he signed an executive order to "counteract the politicians and judges who subvert the law by obstructing and preventing the execution of capital sentences".
Ms Bondi later issued a memo to all Department of Justice employees, which ordered them to revive and reprioritise capital punishment in line with Mr Trump's order.
Mr Thompson's killing has been one of the most talked-about murder cases in the US in recent years.
It prompted an online outpouring of criticism of America's health insurers, support for the accused killer, and threats of copycat crimes, angering authorities.
Mr Mangione is due to reappear in a federal court in Manhattan on April 18.
