Walmart (WMT - Get Report) on Tuesday revealed that former McDonald's (MCD - Get Report) CEO Steve Easterbrook has resigned from the retail behemoth's board, less than 48 hours after he stepped down as the fast-food restaurant giant's head over revelations of an inappropriate relationship with a colleague.

Shares of McDonald's slumped to the lowest level in more than six months Monday, resulting in some $4 billion in lost market value, following Easterbrook's resignation as CEO on Sunday. Easterbrook admitted he had made a "mistake" in pursuing a relationship with a colleague which, while consensual, violated company policy.

His departure was followed by the resignation of David Fairhurst, McDonald's head of human resources, and the appointment of Americas division boss Chris Kepmczinski as group CEO.

"Easterbrook's decision to resign was not due to any disagreement with the company on any matter relating to its operations, policies or practices," Walmart said in a regulatory filing.

Easterbrook, 52, joined Walmart's board in 2018, and was part of the compensation and management development as well strategic planning and finance committees, according to Walmart's website.

McDonald's shares fell 2.7% Monday to close at $188.66, the lowest since early April. In mornign trading on Tuesday, the stock was up 0.84%, or $1.58 a share, at $190.24. Shares of Walmart were little changed at 117.34.