Kroger’s board said it had been alerted to an issue with McMullen’s behavior on Feb. 21, after which it hired an independent outside counsel to investigate the allegations. A special board committee oversaw the investigation that ultimately resulted in McMullen’s departure. McMullen’s conduct did not affect Kroger’s financial performance or its operations, the company said. 

McMullen had been at the helm of Kroger since 2014. Kroger is the largest grocery chain in the U.S. with roughly 2,700 stores and $150 billion in revenue. 

When reached for comment a Kroger spokesperson referred Fortune to the press release announcing McMullen’s exit.

Lead director of the board Ronald Sargent will be interim CEO and chair while the company continues to search for a permanent replacement. Sargent, 69, has extensive retail experience, having previously served as the CEO of office supplies juggernaut Staples. He has been on the board of Kroger since 2006, serving as lead director since 2017. 

As part of his departure, McMullen will forfeit all of his unvested equity and will not be eligible for a 2024 performance bonus, according to an SEC filing. In 2023 McMullen’s total compensation amounted to $15.7 million, that included $10 million in stock awards, according to Kroger’s 2024 proxy statement.

McMullen joined Kroger in 1978 as a stock clerk at a store in Lexington, Ky. Prior to becoming CEO McMullen had already spent roughly two decades in Kroger’s C-suite, first as chief financial officer, then later as chief operating officer. In 2014, when McMullen took the top job, he steered the multibillion-dollar retailer as it navigated the rise of online grocery shopping and through an ultimately failed attempt to merge with grocery chain Albertsons. 

McMullen tried to orchestrate a $24 billion acquisition of Albertsons in October 2022, which would have made the tie-up the largest grocery merger in history. However, after years of wrangling with regulators, who were concerned the merger would lead to too much consolidation in the industry, Kroger eventually walked away from the deal in December. Albertsons sued Kroger for breach of contract. 

McMullen also came to embody a version of the American Dream: He was the first in his family to go to college, then excelled to the highest echelons of the corporate world. 

“My parents had the kind of jobs where if the economy went soft, you got laid off,” McMullen told the Cincinnati Enquirer in 2014. “You don’t want anyone to have the fear I had growing up.”