Sen. Joe Manchin (D-West Virginia) told President Donald Trump to “grow up” after the president issued a series of angry tweets aimed at him.

Trump, who the Senate acquitted on both articles of impeachment the Democratic House brought against him, has been attacking people whom he perceives as his enemies.

The president took to belittling Manchin and other Democrats on Twitter, in a series of tweets after Manchin voted to convict him in the Senate trial. Trump called Manchin “Joe Munchkin” and a “puppet” of the Democratic party.

Manchin had proposed that the Senate should censure Trump.

“I expect — every American and myself would like my president and our president to act like a responsible adult, and he’s not,” Manchin told CNN’s New Day. “For the sake of the country, I hope he does.”

Manchin had been considered the Democrat who was most likely to break partisan lines and vote to acquit Trump. He frequently votes for Trump policies, more so than any other Senate Democrat.

Manchin defended his stance in a statement, claiming that he found sufficient evidence that Trump had abused his power of office and obstructed a Congressional investigation.

Manchin slapped back at the president in an interview on MSNBC, stating that he would not stoop to Trump’s name-calling antics.

“Do you think names bother me? Do I look like I’m small and fragile?” he asked. “Names don’t bother me. The president knows he can’t get to me that way. I’m not going to retaliate. The people want a mature adult — that’s what the president should be. That’s who we want as our president. I want him to succeed. This is not personal with me. I mean, he can call me all the names he wants to. It makes him look like an immature adult. I hope he rises above that. I think it’s best for our country. I believe in our country, I believe in my state of West Virginia as [Sen.] Mitt [Romney] believes in Utah. Good people. And good people finally come — basically they can only pull the wool over their eyes so long. I hope the president changes his ways, I hope he becomes a responsible adult, and I hope he succeeds. I’m going to work with him if we can, but I’m going to be an honest broker.”