Scott Pruitt resigned as head of the Environmental Protection Agency on Thursday, right as federal investigators considered their would-be 19th probe into his conduct as the agency’s most contentious leader.

President Trump announced on Twitter that the EPA’s deputy administrator, Andrew Wheeler, will assume the reins in an acting capacity, starting Monday. Wheeler is perhaps best known for his tenure as an energy lobbyist, representing clients like coal company Murray Energy.

Wheeler was a lobbyist at the firm Faegre Baker Daniels Consulting, which was paid $300,000 or more per year between 2009 and 2017, according to the Center for Responsive Politics.

In short, the EPA is now being overseen by a former coal lackey.

Wheeler is expected to continue Pruitt’s crusade against climate and environmental regulations, and has considerably more experience than his predecessor. He spent four years in the EPA’s Office of Pollution Prevention and Toxics during the Bush and Clinton administrations. In addition, Wheeler also worked as Senator James Inhofe’s general counsel, then continuing on as staff director and chief counsel for the Senate Committee on Environment and Public Works and the Senate Subcommittee for Clean Air Wetlands and Nuclear Safety.

Last month, Wheeler told the Washington Examiner that Pruitt’s job wasn’t in his sights. “While that’s flattering, I am not thinking about it, no,” Wheeler said. “I could have put my hat in the ring for the administrator. I wasn’t interested in that. I am still not interested in that,” he added.

Wheeler may quietly resume Pruitt’s anti-science, pro-industry agenda—in an administration that has rolled back several dozen environmental rules—without the bravado that attracted so much negative attention during Pruitt’s era.

“He will be similar to Pruitt in terms of the agenda—he understands the Trump administration and will carry out the agenda,” Matthew Dempsey, a former colleague of Wheeler’s, told the New York Times. “But he’s been around Washington a long time. He knows how DC works and he does things by the book.”

Still, the former lobbyist isn’t without criticism. According to FOIA records obtained by the Sierra Club, and described by the New York Times:

Last October, soon after Mr. Wheeler was nominated to his position as deputy director, he sent an email to Mr. Pruitt’s chief of staff, Ryan Jackson, a longtime friend, with a headline from The Onion, the satirical publication: “EPA Promotes Pulsating Black Sludge to Deputy Director.”

“Welcome, pulsating black sludge,” Mr. Jackson responded. “I guess I’m going to have to get the cleaning crews to come in more often.”

In response to Pruitt’s resignation, the Citizens for Responsibility and Ethics in Washington, a federal watchdog group, responded: “Good.”

That Pruitt lasted so long is frankly astonishing. The former Oklahoma attorney general was constantly being scrutinized for unethical behavior and activities that toed the law. From extravagant spending on security and travel to nepotism to allegedly destroying federal records—Pruitt racked up dozens of blatant and potential infractions over his short career at the EPA.

"It is extremely difficult for me to cease serving you in this role," Pruitt wrote in his resignation letter to Trump, calling it "a blessing" to have served the president. "However, the unrelenting attacks on me personally, my family, are unprecedented and have taken a sizable toll on all of us."

Wheeler will remain until a replacement—possibly Wheeler himself—is found and confirmed by the Senate.