Mayor Bill de Blasio said Thursday evening that he surprised that his choice to lead the city's school system turned down the offer.

The mayor said Miami-Dade County Public Schools Superintendent Alberto Carvalho and he agreed to make him the next chancellor about a week ago, and that had not changed when they spoke around 8 p.m. Wednesday.

"Never had a situation like this before," de Blasio said during a press conference Thursday evening.

The mayor said a nationwide search for a new chancellor has resumed.

According to de Blasio, Carvalho, who was his first choice to take over for outgoing Schools Chancellor Carmen Fariña, told him the city schools chancellor position was his "dream job."

"He told us repeatedly this was his dream job. And obviously whatever happened here is quite unusual, but if he wasn't interested in the job I don't know why he flew up here and had incessant conversations about all the details and agreed to the release of the information publicly. Something else happened here, and maybe you guys can figure out what it is," de Blasio said to members of the media at the press conference.

He said he did not expect Carvalho to change his mind, as the Miami-Wade superintendent flew to New York City several times, discussed the details of the job and agreed.

De Blasio said Wednesday around 5 p.m., Carvalho was still on board to take the job and said he was comfortable with the city leaking the information to Politico NY, which broke the news.

The mayor said Carvalho had asked that the city match his base salary in Miami, which was higher than Fariña's, and the city agreed.

"He called me during a break in his board meeting and expressed trepidation and concern and, you know, second thoughts," de Blasio said during his press conference Thursday. "I obviously reiterated to him that he had already accepted the job and we had put it out publicly with his agreement."

Carvahlo, it seemed, could not be swayed — and did so in spectacular fashion, with his decision playing out in real-time on TV.

The mayor dismissed the idea that Carvahlo's move was a personal rebuke. If de Blasio was angry at Carvahlo, he kept it in check — unlike his press secretary, who sounded off on Twitter:

"I would not have said it that way," the mayor said, referring to Phillips's rebuke of Carvalho. I'm not surprised people would express their frustration in the heat of the moment, and that's what that was. We are all confused at what happened here."

The mayor would not say Thursday whether a new schools chancellor would be hired by the end of March, when Fariña is set to retire, only saying he would announce her replacement soon.