On Tuesday night at a rally in South Carolina, Donald Trump doubled down on his claim that people in New Jersey cheered after the September 11, 2001, attacks.

The real-estate mogul and GOP primary frontrunner also appeared to mock a journalist for hedging on an earlier report that Trump says corroborates his claim.

Former Washington Post reporter Serge Kovaleski suffers from arthrogryposis, a condition which limits the mobility of his arms — a condition Trump seemed to emulate by awkwardly gesticulating while pretending to quote the reporter, as first noted by Ben Schreckinger at Politico.

While Trump's campaign spokeswoman, Hope Hicks, would not comment on the record to The Post about the incident, a campaign official told the paper that Trump was "not aware of any condition and was not mocking his physical appearance in any way."

But Kovaleski told The Post that he is confident that Trump remembers him and his condition. Kovaleski met with Trump several times when the reporter was covering Trump while working at the New York Daily News from 1987 to 1993.

"The sad part about it is, it didn't in the slightest bit jar or surprise me that Donald Trump would do something this low-rent, given his track record," Kovaleski told The Post.

The New York Times, where Kovaleski is currently a reporter, also had a response to the incident: "We think it's outrageous that he would ridicule the appearance of one of our reporters," a Times spokeswoman told Politico and confirmed to Business Insider.

During his rally speech, Trump pointed again to a September 18, 2001, report from The Washington Post, written by Kovaleski and Fredrick Kunkle.

The report, Trump said, was "written by a nice reporter. Now the poor guy — you gotta see this guy. 'Uh, I don't know what I said. Uh, I don't remember!’ He's going like, 'I don't remember. Uh, maybe that's what I said.' This is 14 years ago, he's still — they didn't do a retraction!"

In his speech, Trump went on to quote a paragraph from the original report.

"Now, that's The Washington Post. Folks, they do nothing for me, they hate my guys, OK? They don't get it," Trump said, before moving off the topic.

The Washington Post has already responded to Trump's use of the 2001 story as a source for his claims. Kovaleski told The Post: "I certainly do not remember anyone saying that thousands or even hundreds of people were celebrating. That was not the case, as best as I can remember."

Kunkle added to Kovaleski's remarks: "I specifically visited the Jersey City building and neighborhood where the celebrations were purported to have happened. But I could never verify that report."

While Kovaleski did not comment to Business Insider for this story, he did reference coverage of the incident on Twitter and retweeted a link to a petition by Daily Beast reporter Gideon Resnick calling for Trump to apologize.

Regarding the petition, Resnick told Business Insider that the imitation bothered him: "[T]here's no way to address this besides either acknowledging that it was open mocking and/or deciding to apologize for it. I don't know Mr. Kovaleski personally, but I think it's important to hold our serious contenders for public office responsible for their behavior."

Following coverage of the incident and statement by The New York Times, Trump began tweeting about the paper:

Update: On Thursday morning, Emilio Garcia-Ruiz, managing editor of The Washington Post, said in a statement: "It's hard for me to imagine a colleague who was more inspirational than Serge when he was with us at The Post. Great reporter. Tremendous colleague. Tireless work ethic. Does not deserve this. No one does."

Donald Trump released a statement on Thursday afternoon, claiming that he has “no idea who this reporter, Serge Kovalski, [sic] is, what he looks like, or his level of intelligence. I don't know if he is J.J. Watt or Muhammad Ali in his prime...” In the statement, Trump also noted that while it was reported that he has met Kovaleski, “despite having one of the all-time great memories, I certainly do not remember him.”

Trump offered an explanation for his physical gestures as well. “I merely mimicked what I thought would be a flustered reporter trying to get out of a statement he made long ago. If Mr. Kovaleski is handicapped, I would not know because I do not know what he looks like. If I did know, I would definitely not say anything about his appearance.”