Kroger CEO Rodney McMullen resigned abruptly after the company board investigated his “personal conduct” and found it counter to their corporate code of ethics.

It’s an abrupt leadership shakeup at the country’s largest supermarket chain, with little detail shared on what exactly led to it.

Kroger on Monday said its board had learned about “certain personal conduct” by McMullen on Feb. 21, just over a week ago. The company says an investigation by outside counsel found the conduct was “unrelated to the business” and did not involve Kroger workers, but still “was inconsistent with Kroger’s Policy on Business Ethics.”

Most recently McMullen had overseen Kroger’s unsuccessful attempt to buy the second-largest supermarket chain, Albertsons. The historic grocery mega-merger faced opposition from the Biden administration’s antitrust officials and several state attorneys general.

After more than two years of trying, the deal died in December after the companies failed to convince multiple courts that they should be allowed to merge to take on bigger rivals such as Walmart. Albertsons abandoned the merger and immediately sued Kroger.

McMullen had led Kroger as CEO since 2014. He originally joined Kroger in 1978 as a part-time stocker. He had earlier served as chief operating officer, chief financial officer and a board director for over a decade.

Kroger is now searching for a new CEO. For now, it has appointed Ron Sargent — Kroger’s lead director and former Staples CEO — as interim chief executive.

In its statement, the company said it still plans to hold a call on Thursday to announce its quarterly earnings and guidance for the year ahead.