Environmental Protection Agency (EPA) Administrator Scott Pruitt testifies about the fiscal year 2018 budget during a Senate Appropriations Subcommittee on Interior, Environment, and Related Agencies hearing on Capitol Hill in Washington, DC, June 27, 2017. / AFP PHOTO / SAUL LOEB        (Photo credit should read SAUL LOEB/AFP/Getty Images)
SAUL LOEB/AFP/Getty Images
Environmental Protection Agency (EPA) Administrator Scott Pruitt testifies about the fiscal year 2018 budget during a Senate Appropriations Subcommittee on Interior, Environment, and Related Agencies hearing on Capitol Hill in Washington, DC, June 27, 2017. / AFP PHOTO / SAUL LOEB (Photo credit should read SAUL LOEB/AFP/Getty Images)
Now playing
02:46
EPA chief Scott Pruitt resigns
trump-firing-resignations-removals-2018-orig-mg_00000615.jpg
trump-firing-resignations-removals-2018-orig-mg_00000615.jpg
Now playing
02:50
Trump administration's big exits in 2018
EAST CHICAGO, IN - APRIL 19:  U.S. EPA Administrator Scott Pruitt makes a statement to the media after meeting residents from and taking a brief tour of the West Calumet Housing Complex on April 19, 2017 in East Chicago, Indiana.  Nearly all the residents of the complex were ordered to move by the East Chicago Housing Authority after the soil and many homes in the complex were found to contain high levels of lead. The area has been declared an EPA superfund site. This was Pruitt's first visit to a superfund site since being named the agency's administrator. The complex is scheduled for demolition.  (Photo by Scott Olson/Getty Images)
Scott Olson/Getty Images
EAST CHICAGO, IN - APRIL 19: U.S. EPA Administrator Scott Pruitt makes a statement to the media after meeting residents from and taking a brief tour of the West Calumet Housing Complex on April 19, 2017 in East Chicago, Indiana. Nearly all the residents of the complex were ordered to move by the East Chicago Housing Authority after the soil and many homes in the complex were found to contain high levels of lead. The area has been declared an EPA superfund site. This was Pruitt's first visit to a superfund site since being named the agency's administrator. The complex is scheduled for demolition. (Photo by Scott Olson/Getty Images)
Now playing
01:44
Lawmakers want probe of Pruitt's secret calendar
WASHINGTON, DC - JANUARY 18: Oklahoma Attorney General Scott Pruitt, President-elect Donald Trump's choice to head the Environmental Protection Agency, testifies during his confirmation hearing before the Senate Committee on Environment and Public Works on Capitol Hill January 18, 2017 in Washington, DC. Pruitt is expected to face tough questioning about his stance on climate change and ties to the oil and gas industry.   (Photo by Aaron P. Bernstein/Getty Images)
Aaron P. Bernstein/Getty Images
WASHINGTON, DC - JANUARY 18: Oklahoma Attorney General Scott Pruitt, President-elect Donald Trump's choice to head the Environmental Protection Agency, testifies during his confirmation hearing before the Senate Committee on Environment and Public Works on Capitol Hill January 18, 2017 in Washington, DC. Pruitt is expected to face tough questioning about his stance on climate change and ties to the oil and gas industry. (Photo by Aaron P. Bernstein/Getty Images)
Now playing
02:19
Why Scott Pruitt may be getting a pass
Pete Marovich and MANDEL NGAN/AFP/Getty Images
Now playing
02:39
Pruitt appealed to Trump to get Sessions' job
EAST CHICAGO, IN - APRIL 19:  U.S. EPA Administrator Scott Pruitt makes a statement to the media after meeting residents from and taking a brief tour of the West Calumet Housing Complex on April 19, 2017 in East Chicago, Indiana.  Nearly all the residents of the complex were ordered to move by the East Chicago Housing Authority after the soil and many homes in the complex were found to contain high levels of lead. The area has been declared an EPA superfund site. This was Pruitt's first visit to a superfund site since being named the agency's administrator. The complex is scheduled for demolition.  (Photo by Scott Olson/Getty Images)
Scott Olson/Getty Images
EAST CHICAGO, IN - APRIL 19: U.S. EPA Administrator Scott Pruitt makes a statement to the media after meeting residents from and taking a brief tour of the West Calumet Housing Complex on April 19, 2017 in East Chicago, Indiana. Nearly all the residents of the complex were ordered to move by the East Chicago Housing Authority after the soil and many homes in the complex were found to contain high levels of lead. The area has been declared an EPA superfund site. This was Pruitt's first visit to a superfund site since being named the agency's administrator. The complex is scheduled for demolition. (Photo by Scott Olson/Getty Images)
Now playing
01:56
Conservatives turn on embattled EPA chief
In this May 16, 2018, photo, Environmental Protection Agency Administrator Scott Pruitt appears before a Senate Appropriations subcommittee on the Interior, Environment, and Related Agencies on budget on Capitol Hill in Washington. Pruitt claimed credit for pollution cleanups done mostly by the Obama administration while flubbing facts about his 2017 condo deal and blaming underlings for his ethical woes. (AP Photo/Andrew Harnik)
Andrew Harnik/AP
In this May 16, 2018, photo, Environmental Protection Agency Administrator Scott Pruitt appears before a Senate Appropriations subcommittee on the Interior, Environment, and Related Agencies on budget on Capitol Hill in Washington. Pruitt claimed credit for pollution cleanups done mostly by the Obama administration while flubbing facts about his 2017 condo deal and blaming underlings for his ethical woes. (AP Photo/Andrew Harnik)
Now playing
02:11
WaPo: Pruitt enlisted aide to get wife a job
Now playing
01:14
Pruitt interrupted by protester holding lotion
WASHINGTON, DC - MAY 16:  EPA Administrator Scott Pruitt, testifies during a Senate Appropriations Subcommittee hearing on Capitol Hill, May 16, 2018 in Washington, DC. The Subcommittee is hearing testimony on the proposed budget estimates for FY2019 for the Environmental Protection Agency.  (Photo by Mark Wilson/Getty Images)
Mark Wilson/Getty Images North America/Getty Images
WASHINGTON, DC - MAY 16: EPA Administrator Scott Pruitt, testifies during a Senate Appropriations Subcommittee hearing on Capitol Hill, May 16, 2018 in Washington, DC. The Subcommittee is hearing testimony on the proposed budget estimates for FY2019 for the Environmental Protection Agency. (Photo by Mark Wilson/Getty Images)
Now playing
02:43
Dems ask FBI to investigate Scott Pruitt
Environmental Protection Agency (EPA) Administrator Scott Pruitt testifies about the fiscal year 2018 budget during a Senate Appropriations Subcommittee on Interior, Environment, and Related Agencies hearing on Capitol Hill in Washington, DC, June 27, 2017. / AFP PHOTO / SAUL LOEB        (Photo credit should read SAUL LOEB/AFP/Getty Images)
SAUL LOEB/AFP/Getty Images
Environmental Protection Agency (EPA) Administrator Scott Pruitt testifies about the fiscal year 2018 budget during a Senate Appropriations Subcommittee on Interior, Environment, and Related Agencies hearing on Capitol Hill in Washington, DC, June 27, 2017. / AFP PHOTO / SAUL LOEB (Photo credit should read SAUL LOEB/AFP/Getty Images)
Now playing
01:23
WaPo: Pruitt used EPA aide to help wife
WASHINGTON, DC - DECEMBER 7:  Environmental Protection Agency Administrator Scott Pruitt testifies before the House Energy and Commerce Committee about the mission of the U.S. Environmental Protection Agency on December 7, 2017 in Washington, DC.  (Photo by Pete Marovich/Getty Images)
Pete Marovich/Getty Images/FILE
WASHINGTON, DC - DECEMBER 7: Environmental Protection Agency Administrator Scott Pruitt testifies before the House Energy and Commerce Committee about the mission of the U.S. Environmental Protection Agency on December 7, 2017 in Washington, DC. (Photo by Pete Marovich/Getty Images)
Now playing
02:06
EPA spent nearly $3.5M on security for Pruitt
EPA Administrator Scott Pruitt testifies before the House Appropriations Committee during a hearing on the 2019 Fiscal Year EPA budget at the Capitol on April 26, 2018 in Washington, DC. (Alex Edelman/Getty Images)
Alex Edelman/Getty Images
EPA Administrator Scott Pruitt testifies before the House Appropriations Committee during a hearing on the 2019 Fiscal Year EPA budget at the Capitol on April 26, 2018 in Washington, DC. (Alex Edelman/Getty Images)
Now playing
01:52
Aide sought used Trump hotel mattress for Pruitt
WASHINGTON, DC - JANUARY 18: Oklahoma Attorney General Scott Pruitt, President-elect Donald Trump's choice to head the Environmental Protection Agency, testifies during his confirmation hearing before the Senate Committee on Environment and Public Works on Capitol Hill January 18, 2017 in Washington, DC. Pruitt is expected to face tough questioning about his stance on climate change and ties to the oil and gas industry.   (Photo by Aaron P. Bernstein/Getty Images)
Aaron P. Bernstein/Getty Images
WASHINGTON, DC - JANUARY 18: Oklahoma Attorney General Scott Pruitt, President-elect Donald Trump's choice to head the Environmental Protection Agency, testifies during his confirmation hearing before the Senate Committee on Environment and Public Works on Capitol Hill January 18, 2017 in Washington, DC. Pruitt is expected to face tough questioning about his stance on climate change and ties to the oil and gas industry. (Photo by Aaron P. Bernstein/Getty Images)
Now playing
02:40
Pruitt target of at least 11 federal probes
 Environmental Protection Agency Administrator Scott Pruitt testifies before the House Energy and Commerce Committee's Environment Subcommittee in the Rayburn House Office Building on Capitol Hill April 26, 2018 in Washington, DC. (Chip Somodevilla/Getty Images)
Chip Somodevilla/Getty Images
Environmental Protection Agency Administrator Scott Pruitt testifies before the House Energy and Commerce Committee's Environment Subcommittee in the Rayburn House Office Building on Capitol Hill April 26, 2018 in Washington, DC. (Chip Somodevilla/Getty Images)
Now playing
02:54
EPA's embattled Pruitt grilled on Capitol Hill
WASHINGTON, DC - NOVEMBER 17:  Environmental Protection Agency Administrator Scott Pruitt leaves after he spoke at an event November 17, 2017 in Washington, DC. Pruitt addressed The Federalist Society's 2017 National Lawyers Convention at the Mayflower Hotel.  (Photo by Alex Wong/Getty Images)
Alex Wong/Getty Images
WASHINGTON, DC - NOVEMBER 17: Environmental Protection Agency Administrator Scott Pruitt leaves after he spoke at an event November 17, 2017 in Washington, DC. Pruitt addressed The Federalist Society's 2017 National Lawyers Convention at the Mayflower Hotel. (Photo by Alex Wong/Getty Images)
Now playing
02:57
Republicans wants answers from EPA chief
(CNN) —  

Environmental Protection Agency Administrator Scott Pruitt has resigned after months of ethics controversies, citing “the unrelenting attacks” on himself and his family, which “have taken a sizable toll on all of us.”

President Donald Trump first tweeted the news Thursday that Pruitt had resigned.

READ: Scott Pruitt’s resignation letter to President Donald Trump

RELATED: EPA chief Scott Pruitt’s long list of controversies

“I have accepted the resignation of Scott Pruitt as the Administrator of the Environmental Protection Agency,” Trump tweeted. “Within the Agency Scott has done an outstanding job, and I will always be thankful to him for this.”

Pruitt’s resignation follows months during which the EPA administrator has been embroiled in one ethics controversy after the next.

It also comes two days after an exclusive CNN investigation revealed a former top aide alleged Pruitt and his staffers held regular meetings to “scrub,” alter or remove controversial events from his calendar. That investigation sparked two Democratic congressman to call Thursday for the EPA inspector general to investigate whether Pruitt committed a federal crime.

Trump said on Twitter that Pruitt’s recently Senate-confirmed deputy Andrew Wheeler will on Monday assume the duties of acting administrator of the EPA.

RELATED: Who is Andrew Wheeler

“I have no doubt that Andy will continue on with our great and lasting EPA agenda. We have made tremendous progress and the future of the EPA is very bright!” Trump tweeted.

On Air Force One en route to Montana later Thursday, Trump voiced support for Pruitt, saying the allegations against his EPA head did not bother him but he accepted the resignation because Pruitt believed they had become a distraction.

“There was no final straw,” Trump said. “Scott is a terrific guy. He came to me and he said, ‘Look, I have such great confidence in the administration. I don’t want to be a distraction.’ “

Trump said Pruitt had approached him about resigning “a couple of days” prior and that the decision was “very much up to” Pruitt.

Asked if there was anything about the accusations against Pruitt that troubled him, the President said, “No.”

“He’ll go on to great things,” Trump said. “He’s going to have a wonderful life, I hope.”

Cloud over Pruitt

An ethics cloud hung over Pruitt for months, as lawmakers from both parties, environmental groups and government watchdogs raised questions about his spending, housing arrangements, security team and raises for political appointees.

Pruitt’s resignation letter to Trump offered regret about leaving the role, but said “unrelenting attacks” had taken a toll.

“It is extremely difficult for me to cease serving you in this role first because I count it a blessing to be serving you in any capacity, but also, because of the transformative work that is occurring,” Pruitt wrote. “However, the unrelenting attacks on me personally, my family, are unprecedented and have taken a sizable toll on all of us.”

He added, “My desire in service to you has always been to bless you as you make important decisions for the American people. I believe you are serving as President today because of God’s providence. I believe that same providence brought me into your service. I pray as I have served you that I have blessed you and enabled you to effectively lead the American people.”

Two EPA officials told CNN they found out about Pruitt’s resignation from Trump’s tweet and had no idea the news was coming.

Pruitt had lost the confidence of many career and political EPA appointees, but many of those eager to see him go had begun to lose hope that he would resign or be pushed out by the President.

“Still in shock to be honest,” one EPA official told CNN. “Incredible that he lasted as long as he did.”

All told, Pruitt left EPA having faced more than a dozen inquiries or reviews into his practices at the agency, including his first-class plane travel, a room that he rented from a lobbyist at $50 per night and the installation of a soundproof booth in his office.

A spokesman for the EPA’s Office of Inspector General told CNN that ongoing or pending reviews of Pruitt will continue, even though he has resigned.

“Any ongoing or pending OIG reviews related to the Administrator and/or his team will continue—regardless of the Administrator’s resignation,” the spokesman said.

But at the same time, Pruitt was one of the most effective implementers of the President’s agenda. Coming into office as a critic of EPA and a climate skeptic, Pruitt moved aggressively to scale back Obama-era moves on climate change, automobile pollution standards and other industrial pollutants.

As recently as June 8, Trump praised Pruitt, telling reporters on the South Lawn of the White House that the EPA administrator was “doing a great job within the walls of the EPA,” and that “we’re setting records.”

“Outside, he’s being attacked very viciously by the press. I’m not saying that he’s blameless, but we’ll see what happens,” Trump said then, and didn’t answer a reporter who asked if Trump was “tired’ of Pruitt.

RELATED: Whistleblower says EPA’s Pruitt kept secret calendar to hide meetings

Pruitt was also involved in some intra-administration maneuvering this spring when he urged Trump to fire Attorney General Jeff Sessions and install Pruitt as the head of the Department of Justice, according to three sources.

But as summer unfolded, the amount of pressure on Pruitt began to near its breaking point as former staffers came forward to air their concerns and accusations about the EPA chief. Former aide Kevin Chmielewski told CNN that Pruitt and his staff kept “secret” calendars and schedules to hide controversial contacts with industry representatives and The Washington Post and The New York Times revealed aspects of testimony Pruitt aides gave to Congress about the EPA administrator enlisted them for personal errands.

Turn to the right

Pruitt, an Oklahoma Republican, came to the job as one of the EPA’s chief critics and was seen as someone philosophically at odds with the agency Trump tapped him to run.

While serving as Oklahoma’s attorney general, Pruitt was one of the chief architects of the legal battle against Obama’s climate change policies and repeatedly sued the agency. He described himself in his biography for that job as “a leading advocate against the EPA’s activist agenda.”

Critics of Pruitt’s nomination drew on his past statements to label him as a “climate skeptic,” a term for someone who denies the scientific link between human activity, climate change and associated impacts.

RELATED: Trump nominees say climate change is no hoax, but still invite skepticism

Along with Trump, who once said that “global warming was created by and for the Chinese,” Pruitt oversaw the efforts to dismantle major climate regulations. Trump announced at the beginning of June last year that he would withdraw the US from the Paris climate accords.

Pruitt announced in October he would withdraw the Clean Power Plan, an Obama-era regulatory structure to limit greenhouse gas emissions on a state-by-state basis.

Inquiries and reviews into Pruitt’s practices at EPA

Pruitt incurred a sizable number of investigations into his spending and practices at EPA, including inquiries by the House, Senate, the EPA itself and the White House. Among them were inquiries into Pruitt’s travel practices, spending within the agency and use of email.

The EPA inspector general is reviewing all of Pruitt’s 2017 travel, which is expected to include multiple taxpayer-funded weekend trips that Pruitt took to Oklahoma, as well as official travel to Italy and Morocco. The inspector general told Congress in a May 2018 letter that he expects the review will be completed by the end of September.

RELATED: EPA watchdog expects to complete Pruitt travel review this summer

A different EPA inspector general review involves Pruitt’s travel practices, suggesting that it will review Pruitt’s use of his round-the-clock security detail, which travels with him even when off-duty on family vacations.

Separately, South Carolina Rep. Trey Gowdy, the Republican who chairs the House Oversight Committee, has asked EPA to justify Pruitt’s use of first or business class seats on flights.

This spring, Gowdy said Pruitt was not forthcoming with records.

RELATED: Rep. Trey Gowdy says EPA didn’t turn over records

There are also multiple inquiries into Pruitt’s lease of a $50-a-night Capitol Hill condo in 2017 from lobbyist Vicki Hart. Hart’s husband, J. Steven Hart, who is also a lobbyist, met with Pruitt at the same time that he was leasing that room.

RELATED: Pruitt met with lobbyist whose wife rented him a room