First, 40 hours of terror. Then people ventured out — and saw their Bahamas in ruins.

The merciless Hurricane Dorian started as most Atlantic Ocean cyclones do, as a tropical wave off the coast of Africa. By Aug. 31, it had intensified into a monster, and throughout the string of islands comprising the Bahamas, people hunkered down or got out if they could. They had seen the Caribbean devastated by major hurricanes in 2017.

Dorian made landfall Sunday on three islands in the northwest Bahamas: Elbow Cay, Great Abaco and Grand Bahama. The Category 5 hurricane had sustained winds of 185 mph. It is not only the strongest storm ever to hit the archipelago nation of 400,000 people, but also tied the record for the most powerful Atlantic hurricane ever to touch land.

The storm then stalled. To the astonishment of meteorologists, the southern eyewall of the storm remained over Grand Bahama for 40 hours. People sent frantic messages for help from the roofs of their submerged homes, and shelters quickly ran out of food. But rescuers were helpless until Dorian moved on.

Josh Morgerman, a veteran storm chaser, was among those holed up as Dorian closed in. He tweeted as the hurricane’s eyewall approached his building, and then went silent. Hours later, he detailed the destruction.

At least 30 people are dead, and officials fear a much greater loss of life. Catastrophic damage is widespread but is most extreme in Marsh Harbour, a city on the east side of Great Abaco exposed to the full brunt of the storm surge, which may have reached 23 feet. The Atlantic Ocean became a bulldozer. Entire neighborhoods were obliterated, boats tossed around as if they were paper cups, and cars and shipping containers shoved into piles.

The northwest Bahamas has become a vast, flooded debris field. Winds that gusted to 220 mph lifted boats from their moorings and tossed them onto what used to be dry land. Roads and airports in the northwest Bahamas remain impassably flooded, and large portions of the islands have become, for now, little more than extensions of the Atlantic.

“The magnitude of destruction is catastrophic,” said Lt. Cmdr. Kristopher Ensley, the captain of the 154-foot Coast Guard Cutter Paul Clark. “It’s tragic.”

The scope of the humanitarian crisis is beginning to emerge. Islanders are struggling without food, power and water. Most of the infrastructure has been flattened, ending for the foreseeable future an economy dependent on tourism. Food may be required for 14,500 people in the Abaco Islands and for 45,700 people in Grand Bahama, the U.N. World Food Programme said.

The U.S. Coast Guard and British Royal Navy have ramped up search-and-rescue operations, plucking dozens of stranded Bahamians and delivering them to Nassau, the nation’s capital. Relatives have gathered there for reunions, and aid workers and volunteers are beginning to mobilize relief supplies. Said Roger Russell, a cameraman living on Grand Bahama: “We are truly faced with a demon here.”