Two people have died and another is wounded following a stabbing on a light-rail train after a man yelled racial slurs at two young women who appeared to be Muslim, police said.
Officers arrested a man who ran from the train in Portland, Oregon, reports said. Police are working to identify the man and the people who were attacked.
Before the stabbing the assailant on the train was ranting on many topics, using "hate speech or biased language", and then turned his focus on the women, one of whom was wearing a hijab, Sergeant Pete Simpson said.
"In the midst of his ranting and raving, some people approached him and appeared to try to intervene with his behaviour and some of the people that he was yelling at," Sgt Simpson said. "They were attacked viciously."
One person was pronounced dead at the scene and another died in hospital, he added. The third person was taken to hospital with non-life threatening injuries.
It wasn't clear why the man was shouting, Sgt Simpson said.
"He was talking about a lot of different things, not just specifically anti-Muslim."
Police do not know if the man has mental health issues or if he was under the influence of drugs or alcohol at the time.
The attack happened on a MAX train as it headed east.
Evelin Hernandez, a 38-year-old resident of Clackamas, Oregon, told The Oregonian newspaper she was on the train when the man began making racist remarks to the women. A group of men tried to quiet him and he stabbed them, she said.
Sgt Simpson said the women understandably left the scene before police were able to talk with them but they would like to hear from them to help fill in what happened.
"It's horrific," Sgt Simpson said. "There's no other word to describe what happened today."