Dozens of Bernie SandersBernie SandersSanders denies tweet about corporate Democrats was dig at Warren Sanders denies tweet about corporate Democrats was dig at Warren Democrats asked to create ideal candidate to beat Trump pick white man: poll MORE delegates walked out of the arena in protest and entered the media tent at the Democratic National Convention minutes after Hillary ClintonHillary Diane Rodham ClintonDemocrats bristle as Hicks appears for daylong Capitol Hill testimony Democrats bristle as Hicks appears for daylong Capitol Hill testimony Trump: 'So sad' Democrats are putting Hope Hicks 'through hell' MORE was declared the party's nominee.

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Shortly after Clinton officially won the nomination, supporters of Sanders, her primary rival, clogged the hallways while chanting “this is what democracy looks like” and "this is our country." From another side of the arena, several people wearing Black Lives Matter shirts also joined in as the group headed outside to the media tent.

When asked if they were being forced out of the arena, one woman clad in a Sanders T-shirt said they were leaving voluntarily, adding, “It’s been a tough day.”

As a group of Sanders supporters entered the media tent, they were swarmed by reporters with cameras and iPhones.

Several people decked out in Sanders attire were also escorted out of the arena by convention staff. One woman screamed that she would not vote for Clinton and said she planned to “leave the Democratic Party.”

The media tent is next to the Wells Fargo Center, where Democratic leaders were urging the party to unite ahead of the fall elections.

"Because we did ... what our delegations sent us here to do. We cast our votes for Sen. Sanders," Michael Lopez, a North Dakota delegate, told The Hill, when asked why they waited until after Clinton was formally the nominee to walk out. 

Delegates indicated that discussions about a walkout had been in the works for days and were part of a deal reached between multiple state groups.

A wall of about a dozen police officers swiftly formed around the path to the arena's exit, with dozens more officers and a handful of Secret Service staffers standing near the rally outside. Additional police officers were called in to prevent more Sanders supporters from accessing the media area.

Asked why they marched into the media tent, Lopez said, "The media is our last hope." 

Sanders delegates have warned for weeks that they are wary of supporting Clinton despite calls from their candidate to back the party's nominee.

Some die-hard Sanders supporters signaled going into the convention that they were hoping to persuade superdelegates to back Sanders and make an eleventh-hour bid to capture the party's nomination. 

Mark Van Landuyt, a California delegate who described the protest as a "massive walkout", said supporters had waited because they hoped they would be able to change the outcome of the process. 

"Bernie Sanders and his supporters are the future. Hillary Clinton is the past," he said. "We think is the risk of putting [GOP nominee] Donald TrumpDonald John TrumpBooker hits Biden's defense of remarks about segregationist senators: 'He's better than this' Booker hits Biden's defense of remarks about segregationist senators: 'He's better than this' Trump says Democrats are handing out subpoenas 'like they're cookies' MORE in the White House by choosing this nominee." 

Most protesters, though, gathered silently around the media tents, with some holding “Bernie 2016” and “Justice for Palestine” signs up against the windows.

Some protesters told reporters they were personally prepared to vote for Clinton but wanted to register their anger with the party, in particular the national committee.

And there were even some Sanders delegates who ended up protesting the walkout.

One Kansas delegate accused the Sanders backers of being "agitators" and "tools of Donald Trump." He engaged in a brief shouting match with another Sanders delegate about the group's actions.

Sarah Ferris and Peter Schroeder contributed.

Updated at 8:28 p.m.