El Paso, Texas (CNN) As Beto O'Rourke left a vigil for the victims of the mass shooting in El Paso on Sunday, his anger boiled over when a reporter asked if there was anything President Donald Trump could say to make things better.

"What do you think? You know the s--- he's been saying. He's been calling Mexican immigrants rapists and criminals. I don't know, like, members of the press: What the f---?" O'Rourke said.

In one moment, the former El Paso congressman had captured the left's furor over how Trump's racist actions are discussed -- and at times explained away -- on the national stage. His comment immediately went viral.

With El Paso now central to national conversations about gun laws, white supremacy and the treatment of immigrants, O'Rourke -- who as a presidential candidate has struggled to recapture the energy of his attention-grabbing Senate run last year -- has an opening to show Democratic voters across the country what made him a star.

In speeches and interviews, he has sought to channel the indignation of his bilingual border community over Trump's racist comments and actions -- which people here say is fomenting hatred and violence.

The 21-year-old white supremacist suspected of carrying out a deadly shooting at a Walmart that killed 22 people wanted to stop a "Hispanic invasion of Texas," according to a political document police believe he wrote. The document echoed some of Trump's rhetoric toward immigrants.

"It's these questions that you know the answers to," O'Rourke continued in his answer to the reporter. "I mean, connect the dots about what he's been doing in this country. He's not tolerating racism, he's promoting racism. He's not tolerating violence, he's inciting racism and violence in this country."

Coming home

As news of the mass shooting in El Paso broke, O'Rourke was in Las Vegas -- 10 minutes from taking the stage at an American Federation of State, County and Municipal Employees forum -- and didn't have his phone on him.

An aide traveling with O'Rourke got a text about the shooting and pulled the former Texas congressman aside. His team spent the following few minutes gathering as much information as possible about the still-developing scene, a source who was in the room said.

His aides, who were already booking flights for O'Rourke and his team back to El Paso, scrambled to figure out what to do. One aide considered asking for a delay to gather more information, the source said. On stage, an emotional O'Rourke called for universal background checks and banning the sale of assault weapons. "Keep that s--- on the battlefield. Do not bring it into our communities," he said.

Shortly afterward, O'Rourke spoke to reporters in Las Vegas.

"Just as I got the news, I called my wife Amy to talk to her. She's driving with my daughter Molly," O'Rourke said as he held back tears. "It's a real reminder of what's most important at the end of the day."

O'Rourke boarded the Southwest Airlines flight, which would make a stop in Phoenix before continuing to El Paso.

In Arizona, a passenger named Chris Morales boarded the flight and struck up a conversation with O'Rourke. He, too, was rushing home to El Paso, because he'd been told his mother, grandmother and aunt had all been shot -- and his aunt had not yet been located.

Amy O'Rourke picked her husband, his aides and Morales up at the El Paso airport and drove the group straight to the hospital. O'Rourke was there with Morales when he learned that his aunt had been located. All three of his family members, though battling serious injuries, had survived.

'Of course he's racist'

O'Rourke's campaign has been cautious not to appear as if he is seeking to benefit politically from a tragedy. The chairwoman of the Republican National Committee, Ronna McDaniel, accused him of trying to use the tragedy to "reboot" his "failing presidential campaign."

But his aides and supporters also argue that this is who O'Rourke is -- and what he'd be saying and doing if he was not running for office.

And his love for his hometown -- and his sense that its values are under assault by Trump -- is, his friends and supporters say, at the core of why he decided to run for president.

"All of this, put together, really strikes at why he's running for office and why he holds the convictions that he does. And I think the debate stage, quite frankly, up to this point hasn't offered him the time necessary to tell the story," said Steve Ortega, an O'Rourke friend and fellow former El Paso city council member. "It's happening in his backyard."

His opposition to what O'Rourke has characterized as Trump's racism animated his Texas Senate campaign last year, in which he shattered fundraising records and came close to ousting Republican Sen. Ted Cruz. That campaign featured O'Rourke amassing huge crowds outside a detention facility in Tornillo, Texas.

In February, as O'Rourke was deciding whether to run for president, Trump visited El Paso as part of his effort to lobby Congress for money to build his border wall. O'Rourke staged a counter-rally that filled a baseball field next door to the venue where Trump held his event, at the same time the President spoke.

Over the last two days, O'Rourke has been a fixture on national television.

On Monday he is due to record a "Pod Save America" podcast and be interviewed in the evening by CNN's Chris Cuomo.

On CNN's "State of the Union" Sunday, O'Rourke said it "cannot be open for debate" that Trump is a white nationalist.

"We've got to acknowledge the hatred, the open racism that we're seeing," he said. "There's an environment of it in the United States. We see it on Fox News, we see it on the internet, but we also see it from our commander in chief. He is encouraging this."

On MSNBC's "Morning Joe" Monday, O'Rourke compared Trump's comments to Nazi Germany, saying he is "talking about human beings as though they are animals; making them subhuman, to make it OK to put their kids in cages."

"The writing has been on the wall since his maiden speech coming down that escalator, describing Mexican immigrants as rapists and criminals. The actions that follow cannot surprise us, and anyone who is surprised is part of this problem right now -- including members of the media who ask, 'Hey Beto, do you think the president is racist?'"

"Well Jesus Christ, of course he's racist," O'Rourke said. "He's been racist from day one -- before day one, when he was questioning whether Barack Obama was born in the United States. He's trafficked in this stuff from the very beginning, and we are reaping right now what he has sown and what his supporters in Congress have sown. We have to put a stop to it."

Clarification: This story has been updated to more accurately characterize what a source told CNN about the O'Rourke campaign's initial response to the El Paso shooting.