Following Defense Secretary James Mattis’ resignation from his White House post, John Kerry bashed President Donald Trump for an administration plagued by unending upheaval.

In a Friday night interview with MSNBC’s Brian Williams, the former secretary of state called out the commander in chief, rebuking him as a crooked politician.

“There’s no secret about how chaotic this is, and increasingly, there is no secret about how corrupt it is, and it’s obviously not just corrupt on a question of criminality; it’s corrupt in terms of keeping faith with American principles, keeping faith with the direction of the country, the way we need to go and the way we need to govern ourselves.”

Citing books like those of Bob Woodward and Michael Wolff, both of whom reveal the inner workings of the White House, Kerry pointed to Mattis’ exit as one of the latest signs of turbulence under Trump’s tenure.

“This is a continuation of a crisis that too many people have been too content to live with.” Kerry said, adding that despite the turbulence, “we have to be resolute ourselves about believing in the strength of our institutions, which I do, and I am convinced that we’ll get through it, but it’s not without great cost.”

He also disavowed the president’s decision to pull out of Syria, which was made just before Mattis announced he was through, something that Kerry noted was not done “because he’s tired.”

“I think just walking away from Syria is an absurd loss of leverage, it is an insult to people who put their lives on the line there to simply say, ‘Oh, OK, I’m out of here.’”

Mattis has previously advocated for a small number of American troops to stay in Syria to continue engaging in counterterrorism initiatives. In his resignation letter, he emphasized serious differences between his and Trump’s views on international affairs, suggesting the president was too friendly toward authoritarianism.

Mattis is set to leave by the end of February.