Iryna Zarutska fled a bomb shelter in Ukraine for the US and had only recently moved in with her partner before she was brutally killed by a career criminal in North Carolina as she sat unsuspectingly on the train.

The 23-year-old was scrolling through her phone as she rode the train home from work at a local pizzeria in Charlotte when she was stabbed to death just four minutes after taking her seat.

She never saw her attacker's face because the cold-blooded killer, who prosecutors have named as career criminal Decarlos Brown Jr., struck her from behind with a pocket knife.

At a press conference on Tuesday, US Attorney Russ Ferguson said that Zarutska's family declined to have her body returned to Ukraine and said she would have wanted to be buried in the US because 'she loved America.'

Officials stepped up charges against Brown to the federal level based on Violence Against a Mass Transportation System, which carries a maximum punishment of the death penalty or life in prison without the possibility of parole.