Albert ‘Kell’ Kelly, a top aide to Environmental Protection Agency chief Scott Pruitt, resigned Tuesday amid scrutiny of his financial dealings with Pruitt that also drew attention to his lifetime ban from banking.

After spending most of his career as a banker in Oklahoma, Kelly joined Pruitt at EPA a year ago to revitalize the agency’s cleanup of toxic sites. Around the same time, the Federal Deposit Insurance Corporation fined him $125,000 for “entering into an agreement pertaining to a loan” without FDIC approval. Soon after he was banned from banking altogether.

Kelly gave no reason for his departure and did not immediately respond to a text message seeking comment.

Two individuals briefed on the decision, speaking on condition of anonymity to discuss a personnel matter, said Kelly was tired of coming under criticism for the FDIC ban and didn’t need the job. One noted that Pruitt did not come out in strong defense of Kelly during his testimony before the House Energy and Commerce environment subcommittee last week.

Pruitt praised Kelly in a statement Tuesday, saying that he has made a “tremendous impact” on the agency’s Superfund program, which aims to clean up hundreds of the nation’s most toxic sites. Kelly helmed a task force that issued recommendations to streamline and speed up those efforts, and he has been instrumental in helping make progress at Superfund sites around the country that had previously languished for years, Pruitt said.

“Kell Kelly’s service at EPA will be sorely missed,” Pruitt wrote.

The resignation comes as Pruitt faces multiple investigations by the agency’s inspector general. He is under scrutiny for ethics and spending issues, including renting a D.C. condo from a lobbyist for below market rate, installing a costly soundproof phone booth and spending millions on his own personal security.

Pruitt and Kelly are fellow Oklahomans and old friends, and Kelly has been a key adviser to Pruitt as the administrator has weathered growing scrutiny. The bank that Kelly led, SpiritBank, loaned money to Pruitt on several occasions, including to buy a home and a stake in a minor league baseball team, according to media reports.

While some viewed Kelly with skepticism when he first arrived at EPA, given his lack of experience in the area, many career officials, residents living near Superfund sites and companies involved in the program came to view him as a competent administrator who solicited input from all sides.

Kelly traveled the country visiting Superfund sites in an effort to identify ways to speed cleanups, some of which have languished for decades. He handed out his email and cellphone to residents in local communities, some of whom described him as one of the more responsive government officials they had dealt with in years.