(CNN)A top adviser to Donald Trump resigned Monday after sending a mocking tweet about just-fired campaign manager Corey Lewandowski, a campaign source tells CNN.
First on CNN: Trump adviser resigns after mocking Lewandowski on Twitter
Michael Caputo, a Trump adviser and head of the communications for Trump's caucus operations team, 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 to campaign chairman Paul Manafort and Rick Gates, according to a copy obtained by CNN.
Caputo also said he deeply respects Trump as well as Manafort and Gates.
"I wish you success in the months ahead. I continue to believe Donald Trump must be elected President in November. With you at the helm, I know he can. Call if I can help," he said.
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," he said.
Caputo had been quietly helping to build Trump's convention's caucus operations team ahead of Cleveland, and was serving as communications director for caucus operations.
The campaign was scheduled to release its caucus operations team on Tuesday, according to a convention source.
The team, part of campaign chairman Paul Manafort's convention operation, will serve as a liaison between Trump's campaign and the national convention staff and has been meeting with RNC staff on the ground in Cleveland for the last two and a half weeks -- marking a big step toward creating a more traditional political machine for a campaign built on nonconformity.
Trump's team is heavily comprised of military veterans, including its director of caucus operations, Ryan Price, who served as an Army Ranger. Price is a longtime GOP campaign operative, and former director of operation for the 2012 Republican National Convention in Tampa.
Price will be assisted by David Urban, a West Point grad and Army Gulf War veteran who had worked as chief of staff for former Pennsylvania Sen. Arlen Specter. Urban will serve as deputy director. Caputo was to serve as director of communications for caucus operations at the 2016 Republican convention.
John Ullyot, a Marine veteran and former adviser to former Sens. John Warner and Specter, who was to serve as deputy director of communications for media relations, will now serve as head of communications due to Caputo's departure.
According to one convention source, the 14-person team will not be involved in any of the campaign's day-to-day communications operations. That will still fall to Trump's spokeswoman -- and only campaign communications team staffer -- Hope Hicks.
Caputo's departure comes amid frustrations over the campaign's lack of hiring so far of a traditional communications team to handle the high volume of media requests that comes with being a nominee for president, according to two sources in and around the campaign.
Trump's convention team is currently in the process of trying to refine Trump's message -- building out its surrogate team ahead of Cleveland under John Wagner, the deputy director of communications for surrogate media. One convention source said they have already added 100 new surrogates, a number that will increase to 250 by the time of the convention.
Wagner has a long list of credentials as retired U.S. Army public affairs officer where he served as an analyst for CENTCOM, an operations officer for NORTHCOM and a media official in Baghdad during Operation Iraqi Freedom.
Wagner, in conjunction with a new rapid-response team, has been prepping daily to respond to attacks -- sitting through "murder boards," committees set up to drill individuals before hitting the media circuit, according to a convention source.
Amber Smith, former spokeswoman for Concerned Veterans of America, has been brought on as press secretary of the rapid response team. Smith is a former Kiowa pilot who served in Iraq and Afghanistan.
Former Trump surrogate and "Apprentice" contestant, Erin Elmore, had been tapped as deputy press secretary, but on Monday, a statement by the Republican National Convention said: "Erin Elmore, who was recently named as a valued deputy press secretary for caucus operations, has left the team and remains active as one of the campaign's surrogate media spokespeople."
Elmore said Monday she could be a "more effective advocate for Donald Trump's election as as surrogate on TV rather than working behind the scenes in Cleveland.
Maricelly Velez, will serve the critical role of deputy press secretary for Hispanic media.
Velez will be responsible for Hispanic outreach during the convention, a position that several sources in and around the campaign say is vital for building unity given various remarks made by Trump during the campaign, including calling Mexican immigrants "rapists" and saying the Mexican-American judge in his Trump University case was incapable of doing his job due to his heritage. Velez had served as assistant director for Hispanic affairs for New York Gov. George Pataki.