The man suspected of carrying out a deadly knife attack on a Ukrainian refugee in Charlotte, North Carolina, has been charged with a federal crime that makes him eligible for the death penalty.

Decarlos Brown Jr, 34, was arrested and charged with first-degree murder over the unprovoked attack on 23-year-old Iryna Zarutska on a train last month. Her killing prompted a widespread debate over crime in American cities.

On Tuesday, the justice department said Brown had also been charged with causing death on a mass transportation system.

Attorney General Pamela Bondi said the department would seek the maximum penalty and he would “never again see the light of day as a free man”.

Graphic video of the killing, released on Friday, has fuelled outrage and reignited debate over US crime rates.

“[Ms Zarutska’s] horrific murder is a direct result of failed soft-on-crime policies that put criminals before innocent people,” Bondi said on Tuesday.

Federal prosecutors in North Carolina disputed accusations of “political grandstanding” during a media conference on Tuesday.

“If mayors can’t keep their trains and buses safe, they don’t deserve the taxpayers’ money,” US Transportation Secretary Sean Duffy said in a statement.

Ms Zarutska fled the war in Ukraine along with her mother and siblings in 2022, and her family wrote in an online obituary that she had “quickly embraced her new life in the United States” and was a “gifted and passionate artist”.

The attack was widely covered in Ms Zarutska’s home country, where news outlets reported shock and sadness over the killing and noted the ongoing debate in the US.

While crime rates in the US remain lower than their pandemic-era peaks, critics have seized on the case to highlight judicial release, and the amount of attention given to the slaying by a number of left-leaning media outlets.

Republicans and conservative commentators questioned why Brown was free despite an extensive criminal history, which according to state records includes convictions for robbery with a dangerous weapon, larceny and breaking and entering.

Other right-wing influencers alleged the crime was racially motivated and claimed that the suspect made a comment about the victim’s race.

The suspect is black and Zarutska was white, however authorities have not outlined a motive and Brown has not been charged with a hate crime.

Brown was reportedly homeless and suffering from mental health issues, and his mother told a local TV station that she had sought to have him involuntarily committed to a psychiatric hospital after he became violent.

In January he was arrested after repeatedly calling the 911 emergency hotline from a hospital, but was later released.

The bustling city of Charlotte receives millions of dollars in federal transport funding – about $50m (£37m) in 2023 – covering roughly 12% of its transit operating budget and more than half of its capital costs, according to the Federal Transit Administration.

“I can’t pull money today from their transit system, I actually have to do an investigation, that’s what the law requires,” Duffy told Fox News. “I guarantee all your viewers that if I find what I think I’m going to find, they are not going to have your public tax dollars going to their public transportation system. Zero, none, nada.”

In a statement, Charlotte Mayor Vi Lyles, a Democrat, said that there had been “a tragic failure by the courts and magistrates” and pledged increase patrols and police staffing on public transportation.A spokesperson for former Governor Roy Cooper, a Democrat, called the slaying “a heartbreaking, despicable act of evil” and told Politico that Republicans had supported cuts in funding to local and state law enforcement.

The current Democratic governor of North Carolina, Josh Stein, said in a social media post: “We need more cops on the beat to keep people safe.”