Massachusetts’ gaming regulatory boss has resigned just one day before a meeting that could affect Wynn Resorts’ Boston casino project.

On Wednesday, Stephen Crosby announced his resignation as chairman of the Massachusetts Gaming Commission (MGC), effective immediately. Crosby’s letter to MGC staff (read it here) said he was leaving with “a profound sense of sadness, regret – and yes, frustration.”

Crosby said he’d decided to leave after the past few weeks saw him twice accused of “prejudging the outcome of the Investigations and Enforcement Bureau’s ongoing investigation regarding the suitability of Wynn Resorts.”

In January, the MGC launched a probe into how much Wynn execs knew of a $7.5m payment their former boss Steve Wynn made to a woman he allegedly sexually assaulted. The MGC is trying to determine if Wynn execs hid the existence of the payment from commissioners while the company was undergoing suitability vetting for its $2.4b Boston-area casino project (now known as Encore Boston Harbor).