A man charged with killing a Ukrainian refugee on a Charlotte light-rail train told his sister in a jailhouse call that "the material used in my body stabbed the lady," according to audio released after his arrest, as officials advanced state and federal charges in the case.

Decarlos Brown Jr., 34, has been charged with first-degree murder in the Aug. 22 killing of 23-year-old Iryna Zarutska, who was stabbed while riding the South End light-rail line. Federal prosecutors on Tuesday added a charge under a statute that forbids violence against mass transportation systems; that charge carries a maximum penalty of death or life in prison without parole.

Surveillance video released by authorities shows a man suddenly lunging at Zarutska from behind as she sat in a carriage shortly before 10 p.m. The footage, prosecutors said, cuts away during the most graphic moments and later shows a man walking through the train clutching a blood-soaked knife. Officials say Zarutska was stabbed three times in her neck and hands.

In a phone call recorded at the Mecklenburg County Detention Center and obtained by reporters, Brown told his sister, Tracey Brown, that "You know that's not me... they've got to investigate the material my body was exposed to." When she asked whether Zarutska had been stabbed, he said, "I hurt my hand stabbing her... I don't even know the lady, I never said one word to the lady at all. That's scary ain't it? Why would somebody stab somebody for no reason?" He also said he was heading "to the hospital to get rid of the material."

U.S. Attorney Russ Ferguson, who announced the federal charge, said prosecutors had determined that the attack occurred on a mass transit system and qualified for the additional federal count. Ferguson said Zarutska's family had declined to repatriate her body to Ukraine and chose to bury her in the United States because she "loved America."

Zarutska, who arrived in Charlotte in 2022 with her mother, sister and brother, had been working evenings at a pizzeria in south Charlotte to support herself as she adjusted to life in the United States, her family said on a GoFundMe page and in statements. Her family described her as a gifted artist who graduated from Synergy College in Kyiv with a degree in art and restoration, and as someone who loved animals and hoped to become a veterinary assistant.

Video from the train shows a mix of responses from other passengers. Prosecutors released footage that appears to show several people filming the bleeding victim; one passenger in a green shirt removed his top and attempted to stem the bleeding. Authorities said nearly one minute and 40 seconds elapsed before a passenger made a significant effort to stop the bleeding.

Prosecutors described Brown as a career criminal during public remarks announcing the charges. Details about any prior convictions were not disclosed at the news briefing. He is being held in the Mecklenburg County Detention Center pending further proceedings.

Police say Zarutska boarded the train after finishing her shift and was stabbed about four minutes after taking a seat. She did not see her attacker before the strike, authorities said.

The killing has prompted public grief and raised questions about transit safety in Charlotte. The restaurant where Zarutska worked posted a tribute saying it had "lost not only an incredible employee, but a true friend" and that it had kept a candle burning in her memory.

Investigators continue to seek additional information about the circumstances that led to the attack. Prosecutors said they will weigh both state and federal evidence as the case proceeds. No trial date has been set, and authorities did not disclose whether Brown has entered a plea.