U.S. President Donald Trump Friday sharply criticized his former secretary of state, Rex Tillerson, after the nation’s former top diplomat described the president as “undisciplined” and someone who suggested policies and actions that violated the law. 

The president, who fired Tillerson by tweet in March of this year after months of turmoil between the two men, returned to twitter Friday to hit back at the former Exxon CEO, calling him “dumb as a rock.”

The president appeared to be responding to Tillerson’s first on-camera interview since leaving office. In the interview, which was taped Thursday evening, the former secretary of state publicly recounted that it was a challenge for him to switch from working at a highly disciplined corporation, and go to work for a president, “who doesn’t like to read, doesn’t like briefing reports.” 

“So often, the president would say, ‘Here’s what I want to do, and here’s how I want to do it,’ and I would have to say to him, ‘Mr. President, I understand what you want to do, but you can’t do it that way. It violates the law.'”
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