President-elect Donald Trump lashed out on Twitter Saturday morning at Democratic congressman and civil rights icon Rep. John Lewis (D-GA), after Lewis said Trump’s presidency was not “legitimate” and that he would not attend the presidential inauguration.

Trump dismissed Lewis’ criticisms of him as “Sad!”

Congressman John Lewis should spend more time on fixing and helping his district, which is in horrible shape and falling apart (not to…… — Donald J. Trump (@realDonaldTrump) January 14, 2017

mention crime infested) rather than falsely complaining about the election results. All talk, talk, talk – no action or results. Sad! — Donald J. Trump (@realDonaldTrump) January 14, 2017

In an interview for NBC News’ “Meet the Press,” released in part on Friday, Lewis said “I don’t see this President-elect as a legitimate president,” citing the intelligence community’s assessment that Russian interference in the 2016 election had helped “destroy” Hillary Clinton’s candidacy.

Lewis also said he would not attend Trump’s inauguration, his first time not to attend the ceremony in his congressional career. He will join a handful of Democratic lawmakers on the sidelines on Jan. 20.

“You cannot be at home with something that you feel that is wrong, is not right,” Lewis said of his decision not to attend.