AUGUSTA — A 56-year-old Augusta man died Sunday, one day after the float plane he attempted to land crashed in the middle of Togus Pond in front of at least 40 people celebrating a wedding anniversary, authorities said.

William H. Green was pronounced dead shortly before 10 a.m. He had been unconscious and on a respirator in the intensive care unit at Kennebec Valley Medical Center, officials said.

Police said Green was alone in the two-seat Cessna, which landed upside down about halfway across the pond around noon Saturday.

Green had flown to Togus Pond from a lake in nearby Manchester, Augusta police Sgt. Robert Vachon said.

“We think he was flying in for the anniversary,” Vachon said. “He made a couple of passes above the pond, and on the third time he tried to land.”

The Federal Aviation Administration was investigating the cause of the crash, Vachon said.