The Oregon man accused of screaming anti-Muslim insults at two women, and then fatally stabbing two men and wounding a third as they tried to intervene on Friday, had a history of making extremist remarks, according to the police and civil rights advocacy organizations. In a statement on Saturday, the Portland police said the attacker, who was identified as Jeremy Joseph Christian, 35, of North Portland, Ore., had been booked into the Multnomah County Jail on charges that included two counts of aggravated murder. The police also said Mr. Christian will be arraigned on Tuesday and could face additional charges. The episode began on Friday when the three men were attacked on a Portland commuter train as they tried to calm Mr. Christian, who, the police said, was ranting and talking disparagingly about the women, one wearing a hijab. The police added that the two women, who were not injured, left the scene and were later identified and contacted by investigators. "It's horrific; there are no other words to describe what happened today," Sgt. Pete Simpson, a spokesman for the Portland Police Bureau, said at a news conference. The police statement also said part of the investigation would focus on Mr. Christian's "extremist ideology." One of the victims, Ricky John Best, 53, died in the train car, the police said. Another, Taliesin Myrddin Namkai Meche, 23, later died at a Portland hospital. A third victim, Micah David-Cole Fletcher, 21, was being treated for serious injuries on Saturday, but the police said his wounds were not considered life-threatening. Mr. Christian has a history of making extremist statements on social media, said Zakir Khan, a member of the Council on American-Islamic Relations who is working to set up a chapter of the organization in Oregon. "From reviewing the suspect's Facebook page, it seems like he was very enthralled with the alt-right and Nazi movements." Mr. Khan added that the two slain men "really sacrificed everything. "They really stood up for the values of the Constitution," he said. In a blog post, the Southern Poverty Law Center, which monitors hate groups, said that "a review of Christian's Facebook page shows an individual all over the political spectrum but indicates that he holds some racist and other extremist beliefs." The post goes on: "Christian also expresses anti-Muslim sentiments on his page. One included a meme, which read, ‘If we're removing statues because of the Civil War ... we should be removing mosques because of 9/11.'" It also says that Mr. Christian has promoted the notion of a whites-only area in the Northwest. Mike Bivins, a freelance journalist in Oregon, said he encountered Mr. Christian last month at a free-speech march being held by conservative groups. During the rally, Mr. Bivins filmed as Mr. Christian yelled racial slurs, made threatening remarks about Muslims, Jews and "fake Christians" and referred to himself as a nihilist. "I didn't think that video would lead to being some sort of evidence of his possible premeditated hate crime," Mr. Bivins said in an interview. On the video, while Mr. Christian is seen yelling, other demonstrators are pointedly disavowing his comments. And on Saturday, Richard B. Spencer, a white nationalist and well-known self-appointed leader of the fringe alt-right movement, condemned the attack. The attack on Friday occurred around 5 p.m. in a train car on Portland's light-rail system. The attacker began yelling — calling Muslims "criminals" — shortly after the two women boarded, said Evelin Hernandez, a train passenger. "He said, ‘Get off the bus, and get out of the country because you don't pay taxes here,'" Ms. Hernandez told KATU-TV. When the men tried to intervene, Mr. Christian pulled out a knife and slashed them, Ms. Hernandez and the police said. The attacker fled the train car but was soon arrested, the police said, adding that a review of Mr. Christian's record did not show any known history of mental illness.