The family of four -- the boy, his parents and his 4-year-old sister -- was on vacation from Nebraska, Demings said. They arrived Sunday.
The parents watched as the alligator attacked the toddler at the Seven Seas Lagoon. The lagoon is connected to a series of canals which feed into large bodies of water.
"The father actually went into the water to wrestle his son from the grips of the alligator," he said. The father suffered minor scratches on his hand but was unsuccessful in getting his son back.
The mother also went into the water, trying to find her child, he said.
"The sad reality of it is it's been several hours, and we're not likely going to recover a live body," Demings said.
He said there is no record of similar incidents in this particular area.
"Everyone here at the Walt Disney Resort is devastated by this tragic accident," said Jacquee Wahler, a vice president at Walt Disney World Resort.
"Our thoughts are with the family. We are helping the family and doing everything we can to assist law enforcement."
Demings said no reports of nuisance alligators have come in the region recently. The alligator is between 4 and 7 feet long, Demings said, adding he's unsure of its exact size.
