Justin Amash, the first Republican in the U.S. Congress to say openly that President Donald Trump has committed impeachable offenses, on Monday fired back at critics, including Trump.

Standing behind his earlier remarks, Amash issued a string of tweets that challenged some of the most common arguments of those who defend Trump over special counsel Robert Mueller's probe of Russian meddling in the 2016 U.S. election.

The new Amash tweets followed his earlier remarks on Twitter on Saturday, when he said that the Mueller report on Russia showed that Trump, a fellow Republican, had obstructed justice.