President Donald Trump is responding to criticism from his former secretary of state Rex Tillerson by calling Tillerson "dumb as a rock" and "lazy as hell."

During a rare public appearance in Houston Thursday evening, Tillerson weighed in on his time in the administration. He called Trump "undisciplined" and said the president "doesn't like to read, doesn't read briefing reports, doesn't like to get into the details of a lot of things."

He also said Trump frequently asked him to do things that he had to explain were illegal or otherwise ill-advised.

Trump says in response that Tillerson "didn't have the mental capacity needed for the job" and that he "couldn't get rid of him fast enough."

He's also praising Tillerson's replacement, Mike Pompeo.

US President Donald Trump on Friday blasted his former secretary of state, Rex Tillerson, in a sharply critical tweet one day after the nation's former top diplomat publicly recounted that the president had tried to do things in a way that violated the law.