The U.S. Coast Guard delivered the news Thursday afternoon that the debris field they located with a robotic device earlier in the day was indeed the remains of OceanGate's Titan submersible vessel.

For the passed four days, the world has been gripped by the story of the missing expedition crew, five men in total. And while a search-and-rescue operation had begun in earnest by Wednesday, with more ships heading to the area today, it turns out the race against an imagined oxygen-supply clock was in vain.

At a press conference, per the Associated Press, the Coast Guard made the grim confirmation that all five men are presumed dead, and the debris field they found earlier, 1,600 feet from the bow of the Titanic, was "consistent with a catastrophic implosion of the vessel."

Rear Adm. John Mauger of the First Coast Guard District delivered the news, saying, "Our most heartfelt condolences go out to the friends and loved ones of the crew."

Mauger said that the remote-controlled vehicle exploring the area had shown them an image of debris from the Titan vessel, including its tail cone.

The five onboard were 61-year-old OceanGate CEO Stockton Rush, Pakistani businessman Shahzada Dawood and his son Suleman Dawood, British billionaire Hamish Harding, and French explorer Paul-Henri Nargeolet. Nargeolet, as has been widely noted, had already been on over 35 dives to the Titanic wreckage site.

Rush, as SFist reported Wednesday, had deep family ties to San Francisco and may have grown up here, at least partly. He attended business school at UC Berkeley, his father passed away in San Francisco on New Year's Day in 2000, and his maternal grandmother was Louise M. Davies, the namesake of Davies Symphony Hall and its main benefactor. Rush and his wife, Wendy Rush, have lived for many years in the Seattle area, where OceanGate is based.

Shahzada Dawood also had a Bay Area tie, as NBC Bay Area reported Wednesday. He served on the board of the SETI Institute, which is dedicated to identifying life across the universe, and is based in Mountain View.

SETI issued a statement Wednesday saying, "The entire SETI Institute community is devastated by the news of our Trustee, Shahzada Dawood and his son, Suleman, who are on board the missing submersible with three other passengers and crew. Shahzada is not only a member of our Board of Trustees but also a dear friend and part of the SETI Institute family."

The chances of human remains being recovered are very slim. As Admiral Mauger told reporters, in answer to that question per the New York Times, "This is an incredibly unforgiving environment down there on the sea floor."

For two days, ships and submersible devices have been searching an area described as the size of Connecticut, hoping to find a sign of life or evidence of the OceanGate vessel's whereabouts. But the possibility of a "catastrophic failure" like the one that seems to have occurred was always there.

The media obtained a letter from deep-sea experts that was written to Rush and OceanGate staff several years ago, expressing grave concern that the company's "experimental approach" to submersible construction could lead to a catastrophe like this. But it may be that all such exploration at extreme depths like this comes with inherent risks, and those who participate in it may as well be more aware of those risks.

“Even the most reliable technology can fail, and therefore accidents will happen," says Nicolai Roterman, a deep-sea ecologist and lecturer in marine biology at the University of Portsmouth, England, speaking to the Associated Press. "With the growth in deep-sea tourism, we must expect more incidents like this."

Related: Founder of Submersible Ocean Exploration Company Missing Near Titanic Wreckage Has SF Roots

Photo courtesy of OceanGate Expeditions