A necropsy is to be performed to try to determine what killed the porpoise, nicknamed Wilbur, and why he washed up at Cape Hatteras National Seashore in the first place, The Virginian-Pilot reported Thursday.

A spokeswoman for the Virginia Aquarium & Marine Science Center in Norfolk said the porpoise died during the night.

A ranger at the Cape Hatteras National Seashore found the sea mammal Tuesday. It was thin and there were scratches on its skin, suggesting that someone had tried to push him back to the water.

Wilbur, wrapped in blankets and foam and covered with wet cloths, was loaded on a plane Wednesday for the trip to The Riverhead Foundation for Marine Research and Preservation on Long Island.

"It's hard, but at the same time we think it was the right thing," said Susan Barco, the Virginia aquarium's stranding response coordinator. "He seemed strong, a good candidate for rehab. We never know, exactly, the history, so it's kind of a shot in the dark. But we keep trying."