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Breitbart reporter Michelle Fields has resigned from the conservative news site over its response to her alleged assault by Donald Trump's campaign manager.

Breitbart reporter Michelle Fields, Washington Post reporter Ben Terris (middle, checkered shirt) and Trump campaign manager Corey Lewandowski (right, background) with Donald Trump. Jabin Botsford / The Washington Post/Getty Images

Three of her colleagues also resigned from Breitbart: editor-at-large Ben Shapiro, national security reporter Jordan Schachtel and Jarrett Stepman, an editor.

In his departing statement on Sunday, Shapiro said the site should be "ashamed" of "their treatment" of Fields, whose allegations of assault came amid escalating violence in and around Trump campaign events.

Schachtel and Stepman followed Monday.

"Breitbart News is no longer a journalistic enterprise, but instead, in my opinion, something resembling an unaffiliated media Super PAC for the Trump campaign," Schachtel said in a statement first reported by Politico. "I signed my contract to work as a journalist, not as a member of the Donald J. Trump for President media network."

I resigned from Breitbart. Was a great run & I wish I could've prevented what it's become. Still many grt ppl there. Sorry to let u all down — Jordan Schachtel (@JordanSchachtel) March 14, 2016

Stepman said in his own statement that Breitbart was "becoming less of a news site and more of a propaganda organization dedicated to the Trump campaign."

JUST IN - Jordan Schachtel and Jarrett Stepman have also resigned from Breitbart pic.twitter.com/ViA1PFuDJr — Hadas Gold (@Hadas_Gold) March 14, 2016

Fields accused Trump campaign manager Corey Lewandowski of grabbing her arm so hard she bruised as she attempted to question the candidate at an event. She wrote an account of the incident, as did a Washington Post reporter who said he witnessed it. Politico also published an audio transcript that purportedly captures the interaction and moments immediately afterward.

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Related: Here's What Trump Supporters Think of Rally Violence

The Trump campaign fought back hard against the allegations. Lewandowski called Fields "delusional" and an "attention seeker," while Trump accused the reporter of having "made up" the incident. Fields, meanwhile, filed a police report.

I can't stand with an organization that won't stand by me: https://t.co/pohxCKScpf — Michelle Fields (@MichelleFields) March 14, 2016

In the immediate aftermath, another Breitbart reporter appeared to question Fields' allegations on Twitter. That reporter was suspended — and the news site's chief executive issued a statement backing Fields and calling on Lewandowski to apologize.

However, the site then published images questioning whether the Washington Post's Ben Terris misidentified Lewandowski as the person who may have physically assaulted Fields. Breitbart later published a piece purporting to show text messages from Lewandowski which it said "prove" he didn't assault Fields.

I guess these just magically appeared on me @CLewandowski_ @realDonaldTrump. So weird. pic.twitter.com/oD8c4D7tw3 — Michelle Fields (@MichelleFields) March 10, 2016

That appeared to be the final straw for Fields, who informed management of her resignation on Sunday night.

“I do not believe Breitbart News has adequately stood by me during the events of the past week and because of that I believe it is now best for us to part ways,” she said in a statement issued to Buzzfeed.

Her colleague Shapiro went further, accusing Breitbart of abandoning and undercutting Fields in order to protect a "bully" — Trump — and his "bully campaign manager."

"Both Lewandowski and Trump maligned Michelle in the most repulsive fashion. Meanwhile, Breitbart News not only stood by and did nothing outside of tepidly asking for an apology, they then attempted to abandon Michelle by silencing staff from tweeting or talking about the issue," Shapiro said in a statement issued to Buzzfeed.

He said the story suggesting Fields and Terris had misidentified Lewandowski — a "poorly-evidenced conspiracy theory" — was the "ultimate indignity."

"This is disgusting," Shapiro said. "No news outlet would stand for it."

Breitbart News has not formally commented on the resignations.

However, the site ran a piece on its homepage Monday with the headline "Ben Shapiro betrays loyal Breitbart readers in pursuit of Fox News contributorship." The piece was later removed but can still be found online.

Breitbart later posted a statement in its place from editor-at-large and in-house counsel Joel Pollak who apologized to Fields and Shapiro for the piece.

"The article was written by me as part of an effort to make light of a significant company event, and was published as a result of a misunderstanding without going through the normal editorial channels," the statement said.

The Fields incident came a week after a Time magazine photographer was thrown to the floor by a Secret Service agent at another Trump rally and amid escalating concerns over the rhetoric used by the Republican frontrunner.

Trump has come under mounting criticism — from Democrats and from Republican rivals — for failing to fully denounce violent incidents at his events and for creating a climate where such incidents can persist.

Those issues were amplified in recent days after video emerged of a man at a Trump rally sucker-punching a protester leaving an event in North Carolina and fights broke out at a cancelled event in Chicago.

Trump himself has said he would like to punch a protester in the face and see another taken out on a stretcher.