President Trump on Sunday made a veiled threat toward House Intelligence Committee Chairman Adam B. Schiff, claiming without evidence that the California Democrat had leaked information from a classified briefing in which a senior U.S. intelligence official told lawmakers that Russia wants to see Trump reelected.

“Somebody please tell incompetent (thanks for my high poll numbers) & corrupt politician Adam ‘Shifty’ Schiff to stop leaking Classified information or, even worse, made up information, to the Fake News Media,” Trump tweeted. “Someday he will be caught, & that will be a very unpleasant experience!”

Trump’s tweet comes more than a week after the intelligence official, Shelby Pierson, told members of Schiff’s committee during a bipartisan briefing that Russia has “developed a preference” for Trump and views his administration as more favorable to its interests, according to people who were briefed on the comments and spoke on the condition of anonymity to discuss a sensitive matter.

Trump became angry after learning of Pierson’s remarks and told acting director of national intelligence Joseph Maguire and another intelligence official that they were being “played,” a senior White House official told The Washington Post. Trump later announced that he was replacing Maguire with a vocal loyalist, Richard Grenell, the U.S. ambassador to Germany.

During the briefing, Pierson also described other steps Russia is taking, including assistance to the presidential campaign of Sen. Bernie Sanders (I-Vt.), according to people familiar with the matter, speaking on the condition of anonymity to discuss sensitive intelligence.

In another tweet Sunday, Trump jokingly suggested that former special counsel Robert S. Mueller III, who led a lengthy investigation into Russian efforts to interfere in the 2016 campaign, should be dispatched to investigate the claims that Russia is seeking to help Sanders win the Democratic nomination.

“Are any Democrat operatives, the DNC, or Crooked Hillary Clinton, blaming Russia, Russia, Russia for the Bernie Sanders win in Nevada,” Trump said. “If so I suggest calling Bob Mueller & the 13 Angry Democrats to do a new Mueller Report, Democrat Edition. Bob will get to the bottom of it!”

Trump maintained in an exchange with reporters outside the White House earlier Sunday that he had not been briefed about any Russian interference efforts. He blamed Schiff and said there should be an investigation into the source of the leak.

Schiff responded with a tweet in which he addressed the president directly, accusing him of “deflection” and telling him: “Your false claims fool no one.”

“You welcomed Russian help in 2016, tried to coerce Ukraine’s help in 2019, and won’t protect our elections in 2020,” Schiff said. “Now you fired your intel chief for briefing Congress about it. You’ve betrayed America. Again.”

Marc Short, chief of staff to Vice President Pence, also sought to pin the blame on Schiff. In an appearance on “Fox News Sunday,” Short argued that the California Democrat’s committee was “selectively leaking out information and often distorting information.”

That claim prompted a swift pushback from host Chris Wallace, who asked Short: “I don’t understand, you’re saying it’s not true and they leaked it?”

Short demurred, saying only that “that was a classified briefing that shouldn’t have been discussed.”

Ellen Nakashima and Shane Harris contributed to this report.