Why did a U.S. destroyer fail to dodge a cargo ship?

There should have been lookouts on watch on the port, starboard and stern of the destroyer Fitzgerald — sailors scanning the horizon with binoculars and reporting by headsets to the destroyer's bridge. At 1:30 a.m. Saturday, June 17, off the coast of Japan south of Tokyo, they could hardly have failed to see the 730-foot freighter ACX Crystal, stacked with more than 1,000 containers, as it closed in.

Radar officers working both on the bridge and in the combat information center below it should have spotted the freighter's image on their screens, drawing steadily closer. And under standard protocol, the Fitzgerald's captain, Cmdr. Bryce Benson, should have been awakened and summoned to the bridge to ensure a safe passage long before the ships could come near each other.

But none of that happened. The Fitzgerald's routine cruise in good weather through familiar, if crowded, seas ended in the most lethal Navy accident in years. Seven sailors lost their lives.

As investigators try to figure out what many veteran seamen describe as an incomprehensible collision, they have plenty of mysteries to unravel. In addition to the questions for the destroyer's crew, there is the peculiar course of the Crystal after the accident, recorded by ship-tracking websites. It raises the possibility that no one was awake, or at least aware of their surroundings, when the two ships hit.

Rather than cut engines, assess the damage and look for ways to assist, the Crystal quickly resumed its former course, steaming toward Tokyo harbor for a half-hour before suddenly executing a U-turn and returning to the crash site — as if the ship's crew had belatedly realized what had happened.

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Investigators have spent the past week surveying the damage, reviewing logs, recovering electronic records — a "black box" aboard the Crystal and stored radar data from the Fitzgerald — and interviewing crew members. There should also be an audio recording from the bridge of the destroyer, like the harrowing tape of a 2012 collision between another destroyer, the Porter, and an oil tanker, in which no one was injured.

Under strict orders not to talk about what they saw that night, the crew of the Fitzgerald is mostly keeping its counsel while grieving the loss of its shipmates. But one sailor, contacted via social media, offered what may endure as an epitaph for the accident.

"All I can say is," the sailor wrote to The New York Times, "somebody wasn't paying attention."

On Friday, Rear Adm. Brian Fort, a veteran warship commander, was ordered to lead the Navy's main investigation of the collision. The multiple investigations now underway — two by the Navy, one by the U.S. Coast Guard, others by the Japanese coast guard and the Crystal's insurers — will probably provide answers. But even if the Crystal crew was asleep, Navy veterans say the far more maneuverable Fitzgerald will likely bear much of the blame.

"This is the kind of thing the Navy is brutally honest about," said Bryan McGrath, who commanded a destroyer in the Atlantic from 2004 to 2006. "To the extent that the Fitzgerald did anything wrong, we'll find out all about it, and there will be consequences."

The two ships sit in ports a short drive apart on the coast south of Tokyo, the 9,000-ton, $1.5 billion Fitzgerald at Yokosuka naval base, its home port, and the 29,000-ton Crystal at Yokohama.

The Fitzgerald has a section of its starboard side caved in, where the Crystal smashed directly into Benson's stateroom, tearing it open and leaving him injured. Sailors had to bend back the door of his cabin to free him and get him inside the ship, the U.S. Naval Institute News reported. Beneath the water line, the container ship's flared bow also tore a large gash in the destroyer's hull, officials said.

As seawater poured in, some 116 crew members were asleep in two flooded berthing rooms. The ship's radio room was damaged and much of its communications gear ruined or left without power.

Sailors fought the flooding for an hour before sending out distress calls, the institute said.

The bodies of the seven men who died were recovered by divers from flooded spaces sealed off to keep the ship from foundering, a wrenching decision by officers in the chaotic aftermath of the crash.

There are many signs that the Fitzgerald had almost no warning of the approaching collision: the fact that the captain was in his cabin and that no shipwide alarm had rousted sailors from their bunks. "As to how much warning they had, I don't know," Vice Adm. Joseph Aucoin, commander of the 7th Fleet, said at a news conference Sunday. "That's going to have to be found out during the investigation."

Less is known about what happened aboard the Crystal, which had been chartered by a Japanese company to bring cargo from Nagoya, on Japan's central coast, to Tokyo. Manned by a Filipino crew, it was far less damaged than the Fitzgerald. On Wednesday afternoon, a large blue tarp hung from a gash in the front of the ship, large scratches were visible on the port side and a section of the bow was crumpled.

Darrell Wilson, a spokesman for Dainichi-Invest Corp., the Crystal's owner, said the company "wishes to offer sincere condolences to the family and friends of those who so tragically lost their lives on the USS Fitzgerald." He declined to comment on whether anyone was awake in the pilot house of the container ship at the time of the collision.

Steffan Watkins, an information technology security consultant who writes for Janes Intelligence on ship tracking, said the path of the Crystal, as posted from its Automatic Identification System, "looks like an automated course." Instead of stopping so the crew could investigate what had just happened, the ship corrected its course and "kept accelerating" toward Tokyo, he said.

"It looks very much like the computer was driving," he said.

But the fact that after more than 30 minutes the Crystal reversed course and returned to the accident scene suggests the captain or crew took control of the ship from the autopilot, Watkins said. "It took them 55 minutes to get back to the spot of the collision, and that's when they called the Japanese coast guard," he said.

Whether the investigations will confirm Watkins' informed speculation remains to be seen. But a number of Navy veterans who joined a lively online debate said that even the most distracted performance by the Crystal's crew could not justify or explain the Fitzgerald's failure to get out its way.

"It looks horrible," said Gary E. Meyer, owner of a tech company in New Jersey, who served on the Navy ship San Diego and posted a YouTube commentary on the accident that got much attention. "You have three lookouts and you're running radar," Meyer said. "That ship can really accelerate and maneuver. It doesn't mean they caused the collision, but they're at fault for not avoiding it."

Steven M. Morawiec, of Sparta, Wisconsin, who spent 22 years in the Navy and many times took charge of his ship at night as the officer of the deck, said the failure to summon the captain was incomprehensible.

"On my ship, if another ship was expected to get within 4,000 yards, you had to have the captain there beside you," he said. "If you didn't wake the captain when you were supposed to, you were toast."

The families of those who perished aboard the Fitzgerald wait for anything that can explain their loss. The bodies are now in the United States and the Navy is conducting autopsies, making funerals hard to plan, said Aly Hernandez-Singer, a cousin of Noe Hernandez, 26, from Weslaco, Texas. Bewildered relatives are grasping at rumors.

"Something ain't right about what they're saying," said Stanley Rehm, the uncle of one of the dead, Fire Controlman 1st Class Gary Rehm Jr., 37, of Elyria, Ohio, whose heroic efforts to rescue others have inspired an online petition to name a destroyer after him. "We got to get to the bottom of this."

Motoko Rich contributed reporting from Tokyo.