Best Buy's Chief Resigns Amid Inquiry Craig Lassig/Getty Images for Best Buy Brian J. Dunn, who became chief of Best Buy in 2009, with shoppers at an Eden Prairie, Minn., store last Nov. 25. Brian J. Dunn, chief executive of the electronics retailer Best Buy, resigned unexpectedly Tuesday during an investigation by the board into what it called his "personal conduct." Mr. Dunn's resignation, less than two weeks after he outlined an ambitious restructuring to revive the struggling store chain, was announced in the morning, with no mention of the investigation. "There was mutual agreement that it was time for new leadership to address the challenges that face the company," a statement from Best Buy's board said at the time. "There were no disagreements between Mr. Dunn and the company on any matter relating to operations, financial controls, policies or procedures," it said. But late in the day, Claire Koeneman, an external spokeswoman for the company, issued a statement that said: "Certain issues were brought to the board's attention regarding Mr. Dunn's personal conduct, unrelated to the company's operations or financial controls, and an audit committee investigation was initiated. Prior to the completion of the investigation, Mr. Dunn chose to resign. The company did not elaborate on the inquiry or the conduct in question. The investigation was first reported by The Star Tribune of Minneapolis and The Wall Street Journal. Larry C. Drapkin, co-chairman of the labor and employment practice at the law firm Mitchell, Silberberg & Knupp, said that an audit committee investigation could mean a number of things, including inquiries into company policy and regulatory issues, but he said it was important not to jump to conclusions. "We sometimes make assumptions that investigations mean it must be bad, and investigations sometimes end with the conclusion that it wasn't," he said. Some investigations require regulatory disclosures; as of Tuesday evening, Best Buy had not filed any new documents with the Securities and Exchange Commission. G. Mike Mikan, a board member and former health care executive, will become interim chief executive as the board searches for a permanent successor. Best Buy, which is based in Richfield, Minn., operates hundreds of giant stores, but people are increasingly buying electronics online. When they do go into chain stores like Best Buy, they often examine products, check prices on mobile phones, then buy from online competitors. "Best Buy has larger-ticket items where people are a little more price-sensitive," said Chris Davey, head of the global commerce business at SapientNitro, a marketing firm. Before the investigation was disclosed, some investors said that Mr. Dunn was doing too little to address online pressures. He said Best Buy would close about 50 of its big-box stores, add hundreds of small Best Buy Mobile locations, increase employee training and bonuses for better customer service and aim to increase domestic online sales by 15 percent in the 12 months that will end in March 2013. Mr. Dunn, who started at Best Buy in 1985 as a salesman, had been chief executive since 2009. Best Buy shares fell 5.9 percent to close at $21.32 Tuesday. Stephanie Strom contributed reporting.