Nov. 9, 2009 (United Press International) -- U.S. casino developer Pinnacle Entertainment (NYSE:PNK) said its chief executive officer resigned two days after an official investigation of his behavior began.

CEO Dan Lee, who was in St. Louis Tuesday, reportedly berated St. Louis County Councilman Steve Stenger after the councilman voted to approve a zoning change that would permit a casino to be built in the northern section of the county. Stenger, however, represents an area in the southern part of the county, where Pinnacle is building a $370 million casino, the St. Louis Post-Dispatch reported Monday.

Reportedly, Lee ran up to the dais during a meeting after Stenger cast his vote to inform the councilman he had just made "the worst move in his political career."

An apology Lee issued did not stop the Missouri Gaming Commission from announcing an investigation into the incident, the newspaper said.

Pinnacle said Lee's resignation was "his own decision." He leaving "to pursue other business interests," the company said.

Pinnacle named Richard Goeglein as an interim non-executive chairman and John Giovenco as interim chief executive officer. Both men have been on the Pinnacle board of directors since 2003.