PORTLAND, Ore. (AP) - The FBI and U.S. Attorney for Oregon are working with police in Portland to investigate the fatal stabbing of two men on a light-rail train who authorities say intervened when another man yelled racial slurs at two young women who appeared Muslim.

The FBI says it's too early to say whether the slayings Friday qualify as a federal hate crime but U.S. Attorney for Oregon Billy Williams said "there's a day of reckoning coming, a day of accountability."

Background: 2 killed in MAX train stabbing

Police on Friday arrested 35-year-old Jeremy Joseph Christian of Portland. He is being held in the Multnomah County Jail on suspicion of aggravated murder and attempted murder.

More: Suspect is a white supremacist with history of violence

Authorities say the stabbing occurred after a man yelled racial slurs at two young women, one of whom was wearing a hijab, and other men attempted to intervene.

Portland Mayor Ted Wheeler decried the charged national political environment surrounding immigration.

Wheeler said, "Violent words can lead to violent acts."

Related: Wheeler calls victims 'heroes'