Barrett met Friday with the board's executive committee and revealed his decision, Stammel said.
"The reason given was just to pursue other opportunities," Stammel said. "He has some things he's working on."
The executive committee informed the full board at a special session Monday, Stammel said.
The board is putting together a committee to find Barrett's successor. In the meantime, Vice President Janet Wall and Managing Director of Sales Mike Messina will oversee daily operations, he said.
Barrett became head of the bureau in 2007; he previously was managing director of Hershey Entertainment & Resorts Co. He remains chairman of the board at Lancaster Science Factory, Executive Director Bob Herbert said.
Attempts to reach Barrett were unsuccessful Wednesday morning.