In a statement, the firm made an abrupt departure from its initial press release that said, "There was mutual agreement that it was time for new leadership to address the challenges that face the company."
The company also said Tuesday that, "There were no disagreements between Mr. Dunn and the company on any matter relating to operations, financial controls, policies or procedures."
That was not exactly the case, The Wall Street Journal reported Wednesday.
The firm now says "an audit committee investigation was initiated" and that "Prior to completion of the investigation Mr. Dunn chose to resign."
Best Buy did not give out any details on what the investigation involved, keeping with a generic statement that, "Certain issues were brought to the board's attention regarding Mr. Dunn's personal conduct."
Dunn had worked at Best Buy for 28 years, rising from a sales clerk to the head of the company.
He became CEO in 2009. The firm said Tuesday that board director G. Mike Mikan would take the helm of the company on an interim basis, while it searched for a new CEO.
Notable deaths of 2014 [PHOTOS]
GM recalls 221,000 Cadillacs and Impalas