Attorney General William Barr, one of President Donald Trump’s staunchest allies, is resigning amid lingering tension with the president over the president’s baseless claims of election fraud and the investigation into president-elect Joe Biden’s son.

In a twitter post of President Donald J. Trump, he said that Barr went to the White House on Monday and submitted his letter of resignation.

Trump has publicly expressed his anger about Barr’s statement to the Associated Press earlier this month that the Justice Department had found no widespread election fraud that would change the outcome of the election.

Trump had long hoped that a Justice Department investigation into the allegedly political roots of the Russia probe would help him damage his Democratic opponent Joe Biden before Election Day.

When Barr made clear that nothing of the sort was forthcoming, Trump fumed publicly that he would be “very disappointed.”

He became angry with Barr again after the election, which Trump has sought to overturn, claiming without evidence that Biden only won because of fraud.