Wynn Resorts was set to take a controlling interest in the casino which was slated to be built at Columbus Boulevard and Reed Streets in South Philly.
In a statement Thursday, Wynn said the company was "fascinated" by legalized gambling in Pennsylvania, but that the project didn't fit their portfolio.
"This particular project did not, in the end, present an opportunity that was appropriate for our company," he said.
He also submitted the project plans to the state gaming control board for approval the same day. A hearing on the project was scheduled for late April.
"I'm stunned," Mayor Nutter said Thursday. He said Wynn was "excited" in their meeting and that there was "not one doubt in my mind after our meeting" that the casino wasn't going to be built.
The mayor says Wynn attorney Kim Sinatra called him Thursday afternoon to make it clear that the city played no role in the deal's termination.
"They certainly wanted to ensure…that this had nothing to do with the city of Philadelphia, but it was about the transaction at hand," Nutter said of the conversation.
Nutter's been a strong opponent to the waterfront casino projects, but says Wynn was receptive to integrating the project into the city's overall riverfront revitalization plan and was interested in hearing the community's feedback.
The termination announcement was an ironic turn of events after Wynn stressed his commitment to the project in early March. At a hearing before the gaming control board in Harrisburg, the casino mogul said he had never backed out of a project this far along in development.
But the board was less willing to trust Wynn, citing an earlier project in New York where he backed out. Wynn called that deal a moment of "temporary insanity."
So does the end of this deal signal an end to a casino in South Philadelphia?
"I just don't know," Mayor Nutter said. "I can't even begin to speculate."
Mayor Nutter said the site's future remains, as it always has, in the hands of the gaming board.
Foxwoods and the Philadelphia project investors have yet to comment on the deal's implosion. They continue to face a daily $2,000 fine for failure to submit project plans on-time.
The gaming board just extended that fine Wednesday even though Wynn submitted the project's plans three weeks ahead of the deadline.