President Trump delivers a speech at the King Abdulaziz Conference Center on May 21 in Riyadh, Saudi Arabia. (Evan Vucci/Associated Press)

President Trump tweeted Monday that the attack on a light-rail train in Portland, Ore., on Friday that killed two men was “unacceptable.” Police say the victims were killed as they confronted a man who was shouting insults against Muslims. Trump recognized the victims for “standing up to hate and intolerance.”

The tweet came from the president's official Twitter account, @POTUS, which is chiefly run by his staff, and not from his personal account, @realDonaldTrump, which he controls. Trump has faced criticism for staying quiet about the attack for so many days, even though he is quick to react to violent acts carried out by Muslim extremists.

According to witnesses of the attack, a white man riding an eastbound MAX train in Portland early Friday afternoon began yelling what “would best be characterized as hate speech toward a variety of ethnicities and religions,” police said. Some of the slurs were directed at two female passengers, one of whom was wearing a hijab, police said. At least two men tried to calm the man down, but “they were attacked viciously by the suspect,” Portland police spokesman Pete Simpson said at a news conference Friday evening.

“It appears preliminarily that the victims — at least a couple of them — were trying to intervene in his behavior, deescalate him and protect some other people on the train when [the suspect] viciously attacked them,” Simpson said.

Jeremy Joseph Christian has been charged in the fatal stabbing of two men who intervened to defend two Muslim women that he was harassing on a Portland, Ore. light-rail train. Editor's note: Video contains graphic content. (Facebook/Larry Blackwood)

The two men killed in the attack were Ricky John Best, 53, and Taliesin Myrddin Namkai Meche, 23. A third victim, Micah David-Cole Fletcher, 21, is being treated for injuries that were not life-threatening.

Police arrested Jeremy Joseph Christian, 35, of north Portland. Local media reports described Christian as a “known white supremacist” in the area, and his Facebook page showed a long history of racist and extremist views.

Amy B Wang contributed to this report.

Destinee Mangum and her 17-year-old friend, who is Muslim and was wearing hijab, were harassed on Portland light-rail train on May 26. The man, Joseph Christian, fatally stabbed two other passengers on board and seriously injured another after they tried to stop him from harassing the women, according to police. (Reuters)