Less than two years after being appointed CEO, Colleen Walker is stepping down as the Eugene McDermott Chief Executive Officer at Dallas’ Perot Museum of Nature and Science. The surprising development was disclosed in a March 30 letter to museum “friends and supporters” from John Jaggers, chairman of the Perot’s board of directors.

“I am writing to inform you that Colleen Walker—in consultation with the Executive Committee—has decided to step down from her position …” Jaggers wrote. “She has agreed to remain in her current role, however, until June 30th to help ensure a smooth and seamless transition.

“It is important to emphasize that this is not an outcome either Colleen or the Board had anticipated, but over time it has become increasingly evident Colleen and the Executive Committee held different views concerning the Museum’s strategic direction and focus,” Jaggers went on. “We agreed, accordingly, that a measured transition to new leadership is warranted.”

A former Miss Colorado who holds an MBA from Harvard University, Walker in June of 2014 succeeded Nicole Small, the Perot’s founding CEO, who retired in late 2013 after 13 years. Walker came to the nonprofit museum after serving for seven years as CEO of the Girl Scouts of Northeast Texas.

In his letter, Jaggers said the museum’s board is appointing a search committee to help select Walker’s successor. The committee will be led by Herman Saenz, the board’s incoming chair.