Bruce Ratner was the mastermind behind Brooklyn's expansive Atlantic Yards project.

NEW YORK CITY-Sending shockwaves through Brooklyn, Bruce Ratner, CEO of Forest City Ratner Cos. and the borough’s biggest developer, reportedly is about to step down. The departure, as revealed Monday in Crain’s New York Business, was the driving force behind the Atlantic Yards complex, including the project’s pivotal offering, Barclays Center, which opened last year. He will be replaced by MaryAnne Gilmartin, EVP and a star at the company.

Representatives for FCRC declined comment and Crain’s reports it is unknown why, or when, Ratner will end his term at the top of the company. However, one source did tell Crain’s, “It will be sooner rather than later, likely in the next few months.” Ratner will continue to be involved, according to an unidentified source.”I wouldn’t expect him to disappear. He’ll still be very much involved at Forest City.”

Ratner spent a decade working on Atlantic Yards and, especially Barclays Center—an arena that’s home to the Brooklyn Nets and the New York Islanders as well as concerts and numerous restaurants. The facility opened last year to great success while a complex of over 12 apartment buildings broke ground on the site. In all, the $4.9 billion Atlantic Yards is expected to comprise 16 buildings providing office and retail space, more than 6,400 units of housing, at varying price-levels, a public plaza and eight acres of landscaped open space.

Gilmartin, who previously served as Forest City’s head of commercial development, oversaw the development of Atlantic Yards. She inherited the project with a distinct disadvantage as her predecessor, James Stuckey, abruptly stepped down in 2007 without familiarizing Gilmartin with the project’s intricacies, according to an earlier report in Crain’s.

But Gilmartin was unfazed. “I’m ready for it,” she told Crain’s at that time. “I’m not afraid of anything.”