Spencer Kirk, CEO of Extra Space Storage, plans to sell as many as 480,000 shares of his common stock in the publicly traded self-storage REIT, with proceeds benefiting philanthropic and humanitarian causes.

In what the company calls a “prearranged stock plan,” Kirk will sell shares of stock he owns outright along with shares he controls through Krispen Family Holdings. The 480,000 shares represent 14 percent of Kirk’s current stake in Salt Lake City, UT-based Extra Space.

Based on the stock’s Nov. 3 closing price of $58.82, Kirk could gain more than $28.2 million if he sold all 480,000 shares.

An Extra Space news release didn’t identify the philanthropic and humanitarian efforts that Kirk will support with the stock proceeds. However, his previous activities might give some indication. From 2004 to 2007, Kirk took a sabbatical from the REIT to run a Mormon mission in Richmond, VA. Also, the Spencer F. Kirk Family Foundation has donated hundreds of thousands of dollars to the Huntsman Cancer Institute at the University of Utah.

According to the news release, Kirk might start selling shares as early as Dec. 3. The stock sale is set to wrap up by Dec. 31, 2016.

As of June 30, Extra Space owned or operated 1,071 self-storage facilities in 35 states, Washington, DC, and Puerto Rico. Those facilities comprise about 715,000 units and about 79 million rentable square feet.