President Donald Trump fired Attorney General Jeff Sessions one day after Democrats regained control of the House and voiced intent to ratchet up pressure on the White House.

Trump used a tweet Wednesday afternoon to make the announcement and install Matthew Whitaker, Sessions’ chief of staff, as the acting attorney general.

“We thank Attorney General Jeff Sessions for his service, and wish him well! A permanent replacement will be nominated at a later date,” the president wrote after sidestepping a question about Sessions’ future during a wild press conference.

Sessions’ ouster came just over an hours after Trump said he liked members of his Cabinet but repeated his line that “everyone leaves” an administration at some point.

Senate Majority Leader Charles E. Schumer of New York reacted to the news in real-time at a post-midterm press conference.

See the Moment Chuck Schumer Learned Jeff Sessions Was Fired

“Protecting Mueller and his investigation is paramount,” Schumer said after his communications director passed him a note. “It would create a constitutional crisis if this were a prelude to ending or greatly limiting the Mueller investigation.”

Schumer declined to answer a question about what he would want to see in an attorney general nominee, while raising suspicions about Trump’s decision to oust Sessions.

“I find the timing very suspect, number one,” he said. “But number two our paramount view is that any attorney general, whether this one or another one should be able to interfere in the Mueller investigation in any way.”

The president’s frustrations with his attorney general have at times publicly boiled into what appeared to be anger over many issues related to the Justice Department’s Russia election meddling probe.

Trump wanted Sessions to fire special counsel Robert Mueller and openly panned him for not appointing a second special counsel to investigate 2016 Democratic presidential nominee Hillary Clinton.

The president at one point fired off a list of tweets during Sessions’ tenure criticizing the attorney general.

“Why is A.G. Jeff Sessions asking the Inspector General to investigate potentially massive FISA abuse. Will take forever, has no prosecutorial power and already late with reports on Comey etc. Isn’t the I.G. an Obama guy? Why not use Justice Department lawyers?” he wrote Feb. 28, adding of the former GOP senator’s judgment: “DISGRACEFUL!”

Sessions fired back later that day, saying “as long as I am the Attorney General, I will continue to discharge my duties with integrity and honor, and this department will continue to do its work in a fair and impartial manner according to the law and Constitution.”

Trump’s own description of his frustrations with Sessions, who was the first Republican senator to endorse Trump’s candidacy, began shortly after Sessions took office. The attorney general recused himself from the Justice Department’s investigation into Russia’s meddling in the 2016 election due to meetings with a Russian diplomat he did not disclose during his Senate confirmation process.

The departure will likely be interpreted by Democrats and Trump critics as the president making a move against the Justice Department special counselor for the Russia investigation because Sessions would not fire Mueller, and could allow Trump to appoint an attorney general or acting AG who would fire Mueller.

What might happen next could be explosive. Sessions has many Republican friends in the Senate.

Despite initially defending Sessions, as the Justice Department’s Russia probe appeared to move deeper inside Trump’s inner circle to his eldest son and son-in-law, the president began to grow disenchanted with his attorney general.

Calling the recusal “very unfair to the president,” Trump decided to take his frustrations public during a July 19 interview with the New York Times, a rare move by a sitting president against an attorney general — or any Cabinet member.

“Sessions should have never recused himself, and if he was going to recuse himself, he should have told me before he took the job and I would have picked somebody else,” Trump told the newspaper.

“How do you take a job and then recuse yourself?” said Trump. “If he would have recused himself before the job, I would have said, ‘Thanks, Jeff, but I’m not going to take you.’

“It’s extremely unfair — and that’s a mild word — to the president,” Trump said.

From there, Trump began steadily hammering Sessions on Twitter.

On July 25, the president wrote the attorney general “has taken a VERY weak position on Hillary Clinton crimes (where are E-mails & DNC server) & Intel leakers!”

Senate Republicans, including the two leaders of the Judiciary Committee, initially warned Trump against pushing Sessions out. But as the duo’s relationship soured, both Chairman Charles E. Grassley of Iowa and Lindsey Graham of South Carolina relented, with the former saying he is confident the panel can find time to move what will be a politically charged nomination.

Sessions had a memorable stint as the country’s top law enforcement official since he left what some experts call one of the safest Senate seats. He had represented Alabama in the chamber since 1997. White House officials would privately say they would remind the president that the attorney general was implementing his agenda likely better than any other Cabinet official when Trump would grow angry with him.

For instance, Sessions moved to lengthen sentences for drug-related charges and moved to restrict federal funding to so-called immigration “sanctuary cities,” among other decisions that riled Democrats and even troubled some Republicans.

He also was the central figure in a memorable June 13 Senate Intelligence Committee hearing that was part of the panel’s ongoing Russia meddling probe.

Trump’s first attorney general aggressively denied any involvement that day to collude with Russian officials to interfere in the 2016 president election on Trump’s behalf.

“The suggestion that I participated in any collusion” that would hurt the United States, which “I have served for 35 years,” an emotional Sessions said, “is an appalling and detestable lie.”

Jennifer Shutt and Lindsey McPherson contributed to this report.