After months as the target of President Trump’s dissatisfaction, Homeland Security Secretary Kirstjen Nielsen is likely to be fired, sources close to the president told the New York Times.

According to national security expert Juliette Kayyem, this West Wing shakeup comes after Trump expressed anger that Nielsen, a notorious immigration hardliner, was not tough enough on the issue.

“Nielsen really could not have done anything more, and in fact, in my mind, did too much,” Kayyem said in an interview with Boston Public Radio Wednesday. “She not only lied to the American public about whether there was a policy of family separation at the podium — just flat-out lied — she initiated and embraced and became the spokesperson of a policy that was so morally corrupt and so poorly planned that we still have 100 children not reunified with their parents four months after the program stopped.”

According to Kayyem, Trump’s campaign promises to build a wall and crack down on illegal immigration show a lack of depth in planning.

“We always thought that Trump’s simplicity of demanding a wall was shorthand and demanding as a campaign issue, and we’ve now come to realize that his depth is not much further than a wall,” Kayyem said. “That’s how he actually thinks that one deals with migration patterns — unlawful and lawful.”

Juliette Kayyem is an analyst for CNN, on the faculty at Harvard’s Kennedy school and CEO of ZEMCAR.