Unsuccessful presidential candidate and Senator Bernie Sanders (I-Vt.) weighed in on President Donald Trump’s bombshell announcement from Tuesday morning that he had replaced Rex Tillerson as Secretary of State with former CIA Director Mike Pompeo. Sanders said it was a bad idea as it does not indicate “stability and leadership” to the world.

President Trump thanked Tillerson for his service Tuesday, saying he had a good relationship with Tillerson but that they did not always agree. Trump said there was more “chemistry” between himself and Pompeo, however, and he felt the switch was the right thing to do.

Sanders thought otherwise. He tweeted: “Firing the secretary of state by tweet is no way to run a foreign policy. Countries around the world are looking to the U.S. for signs of stability and leadership. Trump is sending the opposite message.”

Sanders indication that Tillerson just found out about his replacement by tweet is unverified. According to the Washington Post, “Trump last Friday asked Tillerson to step aside, and the embattled top diplomat cut short his trip to Africa on Monday to return to Washington.”

Tillerson himself said he’d spoken directly to the President about the transition, and Trump said he and Tillerson had talked about the possibility of the change at other times in the past.