During a rally in South Carolina on Tuesday (Nov. 24,) US presidential hopeful Donald Trump mocked a reporter suffering from a disability that freezes one’s joints in place. Jerking his arms like robot, and bending his right wrist, Trump told the crowd, “You’ve got to see this guy.”

Trump was talking about Serge Kovaleski, and an article the reporter wrote after the Sept. 11, 2001 terrorist attacks in the United States (at the time Kovaleski worked for the Washington Post):

Said Trump, “Now, the poor guy—you’ve got to see this guy, ‘Ah, I don’t know what I said! I don’t remember!'”

Kovaleski, who now works for the New York Times, was born with arthrogryposis, a condition in which joints become permanently flexed or extended (clubfoot is one common symptom). His right wrist is bent and he carries his right hand at an angle.

The article in question says “lawmakers detained and questioned a number of people” who were allegedly seen celebrating the Sept. 11 terrorism attacks. Trump and his supporters say it is proof of Trump’s debunked claims that he saw “thousands and thousands” of Arabs celebrating after the attacks. Kovaleski told CNN this week a lot of that reporting has “faded from memory” but that he doesn’t recall thousands or even hundreds of people celebrating after the attacks.

Kovaleski covered Trump for the Daily News from 1987 to 1993. After he was mocked, he told the Washington Post he was sure the GOP candidate remembered his condition. The New York Times called the mockery “outrageous” in a statement to Politico, and disgust for Trump quickly mounted on social media, including from Republicans and Trump fans.

Trump has not apologized for the mocking impersonation. Instead he recently took to Twitter to attack the New York Times.