Sen. Bernie Sanders (I-VT) speaks at a campaign rally at Arizona Veterans Memorial Coliseum on March 5, 2020 in Phoenix, Arizona.There were several disruptions during the rally, including a white nationalist brandishing a Nazi flag. The Arizona Democratic primary will be held on March 17. Caitlin O'Hara/Getty Images

An unknown individual unfurled a Nazi flag bearing a swastika at an Arizona rally for Sen. Bernie Sanders on Thursday night.

With the 2020 Democratic field narrowed to Sanders and former Vice President Joe Biden, the Vermont senator could become the nation's first Jewish president.

"It is horrific, it is beyond disgusting, to see that in the United States of America, there are people who would show the emblem of Hitler and Nazism," Sanders said on Friday.

One rallygoer told BuzzFeed News that the unidentified man also shouted "Heil Hitler" and performed the Nazi salute as Sanders spoke.

Video of the incident was shared on social media Thursday night, with users reacting in horror to the hateful symbol.

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An unidentified man disrupted a Bernie Sanders rally in Phoenix, Arizona by waving a large Nazi flag from the upper stands as the politician who could potentially become the nation's first Jewish president spoke to thousands of supporters on Thursday night.

Video taken by a Snapchat user showed an individual in a white shirt unfurling the flag behind Sanders.

The hateful symbol appeared at a time when the United States has grappled with a resurgence of anti-Semitic violence, such as the 2018 synagogue shooting that killed 11 Jewish worshippers in Pittsburgh.

Speaking to reporterson Friday, Sanders condemed the display at his rally and called it "unspeakable."

"It is horrific, it is beyond disgusting, to see that in the United States of America, there are people who would show the emblem of Hitler and Nazism," he said.

On Thursday night, cheers and screams for the candidate turned into horrified boos as the crowd saw what was happening. Sanders stopped and turned around to see the cause of the uproar, but the flag had been pulled out of view by then.

Sanders said on Friday that he did not initally see the Nazi banner, but was told about it later.

The man also shouted "Heil Hitler" and waved his hand in a Nazi salute, BuzzFeed News reported.

"He never put his arm down," attendee Ron Mack, who was seated nearby, told BuzzFeed."Everybody was in disbelief."

ABC 15 reporter Nicole Grigg, who was outside the arena, filmed a man in a white shirt being ejected from the rally, and tweeted that she believed it was the same man who had been kicked out for waving the swastika.

Grigg's video shows the man shouting a racist slur at a security guard as he walked away from the arena.

State troopers were alerted to the disturbance by the Coliseum's security, and "the crowd turned on the man as troopers climbed the stairs to reach him," Arizona Department of Public Safety spokesman Bart Graves told Insider.

The man fled and dropped the flag when he saw the state troopers approach.

Troopers could not find the man on the property, but if they had he would have been cited for trespassing, according to Graves.

"I never thought I would have seen a swastika at a political event," Sanders national campaign surrogate Brianna Westbrook told the Washington Post. "It's gross."

The swastika's appearance drew outrage from beyond the Sanders campaign.

"I don't care who you're supporting, attacks like this against a man who could be the first Jewish President are disgusting and beyond the pale," former Vice President Joe Biden tweeted. "Hatred and bigotry have no place in America — and it's up to all of us to root out these evils wherever they're found."

Bend the Arc: Jewish Action, a progressive Jewish political advocacy group, called the Nazi banner's appearance "horrifying" and demanded "it must be condemned all over the news."

Just hours earlier, Sanders' campaign had released a video that highlighted the candidates' heritage and featured Jewish supporters.

"I can remember vividly as a kid looking at picture books about what happeed in the Holocaust," Sanders said in the video, adding that his father's family was "wiped out by Hitler."

"I would be very proud to be the first Jewish president," Sanders wrote in at tweet accompanying the video.