Kroger KR -1.66%decrease; red down pointing triangle Chief Executive Rodney McMullen resigned from the company following a board investigation into his personal conduct, ending a more than four-decade career at the grocery chain.

Kroger, the biggest U.S. supermarket chain by sales, said Monday that while the conduct was unrelated to the company’s business, it was inconsistent with its ethics policy. Lead director Ronald Sargent will serve as chairman and interim CEO while the company searches for a permanent replacement for McMullen.