Brian Dunn has handed the baton to a company director, former UnitedHealth Group Inc CFO G. Mike Mikan, who’ll serve as interim CEO while the board looks for a long term replacement. Best Buy founder Richard Schulze is still there as chairman. The company announcement notes that “there were no disagreements between Mr. Dunn and the company on any matter relating to operations, financial controls, policies or procedures” — suggesting that there was friction over a different issue.  The announcement quotes Dunn as saying that he has “enjoyed every one of my 28 years with this company, and I leave it today in position for a strong future.” Still, the news is a surprise: It comes less than two weeks after Dunn unveiled an ambitious plan for Best Buy to focus on mobile phone sales as it cuts total retail space. The consumer electronics chain said it will close 50 of its big box stores in the U.S. in the fiscal year that ends in February and remodel others to emphasize phone, video, and broadband services. Meanwhile, the chain will open 100 smaller Best Buy Mobile stores; it expects to have as many as 800 in 2016, up from 305 today. The goal is to cut costs as the company tries to find its niche in a market where consumers increasingly buy electronics online, including from mega e-retailer Amazon. Best Buy shares are down 2.6% in late morning trading, and -25.6% over the last 12 months.