Michael Caputo, an adviser to Donald Trump, resigned after he tweeted mocking the just-fired campaign manager Corey Lewandowski.
According to CNN, Caputo tweeted "Ding Dong the witch is dead" following the news that Lewandowski had been fired.
"I regret sending out a tweet today alluding to the firing of Corey Lewandowski. In hindsight, that was too exuberant a reaction to this personnel move. I know this is a distraction from the kind of campaign you want to run, so I'm resigning my position as director of communications for caucus operations at the 2016 Republican National Convention. Let's make this immediate," Caputo wrote in a letter.
Caputo later told CNN that "falling on the sword is what you do if you mess up. Unforced errors have no place on a general election campaign for the White House.
Earlier, Trump fired his controversial campaign manager Corey Lewandowski, unleashing a major shake-up.
Ivanka Trump, the candidate's daughter, played a pivotal role in convincing Trump to take action against Lewandowski. She had been critical of Lewandowski for months and this was not the first time that she had leaned on her father to part ways with his top aide.
"The Donald J. Trump Campaign for President, which has set a historic record in the Republican Primary having received almost 14 million votes, has today announced that Corey Lewandowski will no longer be working with the campaign. The campaign is grateful to Corey for his hard work and dedication and we wish him the best in the future." Trump's spokeswoman Hope Hicks said in a statement.