A rep for billionaire Donald Trump’s presidential campaign took aim at billionaire Mark Zuckerberg after the Facebook CEO appeared to criticize Trump’s immigration policies.

At Facebook’s F8 developer conference Tuesday, Zuckerberg made a reference in his opening keynote to Trump’s plan to build a massive wall between the U.S. and Mexico.

“I hear fearful voices calling for building walls and distancing people they label as others,” he said. “For blocking free expression, for slowing immigration, reducing trade, and in some cases around the world even cutting access to the Internet… Instead of building walls, we can build bridges.”

A Trump spokeswoman on Wednesday accused the Facebook CEO of “self-righteousness” and said that he was out of touch with ordinary Americans.

“I think I’ll take Mark Zuckerberg seriously when he gives up all of his private security, moves out of his posh neighborhood, and comes live in a modest neighborhood near a border town, and then I’m sure his attitude would change,” Katrina Pierson said on CNBC’s “Squawk on the Street” Wednesday.

“The CEOs in Silicon Valley should focus on innovation and jobs and their businesses and let the politicians make their policies,” she added.

Facebook declined to comment.

Trump, currently the front-runner in the Republican presidential primary, has been quick to attack critics or those he believes have treated him unfairly, including Fox News anchor Megyn Kelly.

Zuckerberg, 31, currently has a net worth of $47.7 billion, while 69-year-old Trump’s holdings stand at $4.5 billion, according to Forbes.

In December, Zuckerberg and his wife, Dr. Priscilla Chan, announced that they would donate 99% of their Facebook shares — worth about $45 billion at the time — to philanthropic initiatives.