LAKE BUENA VISTA, Fla. -- The 2-year-old boy who was grabbed Tuesday night by an alligator near a Walt Disney World resort hotel is believed dead, Orange County Sheriff Jerry Demings said Wednesday. Demings noted that it has been 15 hours since the attack and rescue officials are trying to recover the body.

The boy's family was at movie night outdoors at the Grand Floridian resort when around 9 p.m. the boy waded into about a foot of water in a lagoon, authorities have said. Witnesses, including the boy's horrified parents, tried to save him. His father jumped in and tried to pry the gator's mouth open. His mother jumped in, too.

But it was too late. The child was dragged underwater in the Seven Seas Lagoon, witnesses told authorities. The lagoon is connected to a series of canals that feed into large bodies of water, according to Florida Fish and Wildlife Conservation Commission Executive Director Nick Wiley.

A search began for the boy immediately, with boats from Disney searching along with law enforcement.

By midmorning Wednesday, Disney had closed all beaches in its resort area "out of an abundance of caution" following the attack, a Disney representative said.

Wiley said the child was on the edge of the lagoon when the alligator attacked, according to the boy's family. He cautioned that the investigation is still in an early stage and officials need to interview at least two other families who may have witnessed the attack.

Demings specifically said that the child was "wading ... along the lake's edge at the time that the alligator attacked."

Parents rush into water to save son

The father suffered minor scratches on his hand trying to save his son.

"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.

A handful of people witnessed the attack and supplied police with information. Witnesses said the family was on the beach, and the boy's sister was in a playpen about 20 to 30 yards from the water, according to Demings. The toddler was nearby, wading in the water.

There are "No Swimming" signs at the lagoon, and no one else was in the water at the time of the attack besides the child, Demings said.

Declan Salcido, who was vacationing at the resort with relatives from San Jose, California, said the "No Swimming" signs are visible "from any vantage point."

The lagoon is not for recreational swimming.

"This is Florida, and it's not uncommon for alligators to be in bodies of water," Demings said.

Many on social media lambasted the child's parents, while others urged compassion.

Some people said a "No Swimming" sign is hardly sufficient if alligators could be lurking.

Unusual attack

"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.

Jeff Corwin, a noted national animal expert, said he was surprised this happened so close to a highly regulated area but noted there are millions of alligators in Florida. Disney has many thousand acres. An alligator could make its way, undetected through some swamp and marsh into a lagoon near where people congregate.

A gator that size would be unlikely to attack an adult, he said, but a child would be more vulnerable.

When a gator bites down, his jaws snap closed, with thousands of pounds of force, Corwin said. "I can't imagine the terror on these people's minds trying to manage this," he said.

As of April, only one other major alligator attack has been reported this year, according to Florida Fish and Wildlife Conservation Commission. That person survived the attack, but required medical care.

In 2015, there were nine major unprovoked attacks with one fatality.

The search

The Reedy Creek emergency services call center first received a report about the attack at 9:16 p.m. ET Tuesday.

The attack occurred on a sandy waterfront area outside the hotel near the Seven Seas Lagoon on the property.

Authorities do not plan to stop the search until the boy is found or recovered.

Helicopters, sonar, marine units and an alligator trapper are being used in the rescue effort. Divers are on standby.

"We're not leaving until we recover the child," Demings said.

At least 10 emergency vehicles were on the scene, and the beach was cordoned off.

Salcido said he saw seven or eight boats searching the waters, including two Disney security boats and pontoons owned by the company to take guests out on the water for fireworks.

The Florida Fish and Wildlife Conservation Commission, which is conducting a parallel investigation and participating in the search, has deployed an alligator trapper, officer Chad Weber said.

"We're putting every effort into locating the child and trapping this alligator," he said. "We'll be here with them until there's a resolution."

A helicopter with a search light scoured the lagoon as a handful of Disney employees ushered people away from the sidewalks overlooking the beach.

The week

It has been a tragic week for the Orlando area. A gunman massacred 49 people early Sunday at an Orlando gay club in the deadliest mass shooting in U.S. history.

A day before the rampage, a man shot singer Christina Grimmie as she was signing autographs following a concert.