There was no miracle ending for the story that gripped so much of the world this week.

Four days after OceanGate Expedition's 22-foot submersible went missing on its way to tour the wreckage of the RMS Titanic, the U.S. Coast Guard announced that the vessel had suffered a deadly implosion.

USCG Rear Adm. John W. Mauger said June 22 that the families of the five people aboard were immediately notified once officials and experts had concluded the craft was lost.

"I can only imagine what this has been like for them," Mauger said. "I hope that this discovery provides some solace during this difficult time." 

OceanGate, whose CEO and founder Stockton Rush was piloting the June 18 expedition, called the five men who were presumed dead "true explorers who shared a distinct spirit of adventure, and a deep passion for exploring and protecting the world's oceans."

Meanwhile, just thinking about their fate is enough to cause hyperventilating. The search for the sub Titan turned into a horror show unfolding in real time, the most chilling detail being not what officials described as "limited rations" of food and water onboard, but the 96-hour oxygen supply they set off with.

And as soon as news of the missing sub broke, tragic and downright bizarre details started piling up alongside reports of long-standing concerns about the safety of OceanGate's overall operation, including from previous Titan passengers.

OceanGate has not said anything about the resurfaced criticisms this week. The company did not return E! News' or NBC News' requests for comment.

"This is a mature art," Titanic director James Cameron, who made 33 dives to the 111-year-old wreckage that inspired his 1997 blockbuster, told ABC News after Titan's fate was known, "and many people in the community were very concerned about this sub."

We may only be at the tip of the iceberg when it comes to the full story surrounding the events of the past week, but this is how it's unfolded so far:

What is OceanGate Expeditions?

Rush wanted to see what was left of the Titanic—which claimed the lives of his wife Wendy Rush's great-great-grandparents Ida and Isidor Straus when it sank in 1912—before it decayed into nothingness. And he felt there was a market to give paying customers the same chance.

"It made perfect sense," he told Deutsche Welle in 2019. "We just had to make the submersible to get there."

The Seattle-based aerospace engineer (and once-aspiring astronaut) started developing plans for a sub in 2003 and started OceanGate in 2009, his goal being to make several dives a year. Wendy's LinkedIn bio says that she's the company's communications director, as well as an expedition team member.

What was it like onboard the submersible Titan?

Rush touted the pioneering aspects of Titan, which in December 2018 became the first private company-owned sub with a human aboard to dive the average depth of the ocean and beyond, to 13,000 feet, a little deeper than the Titanic wreckage. 

"We realized that we had to have at least the capability for four people, which nobody did," he told Deutsche Welle. "The reason is you have to have a pilot and an expert, because having somebody who's passionate and knowledgeable about what you're looking at completely changes the nature of the dive. And then if you're going to take somebody to go see the Titanic it's going to be the most life-changing experience for them. They won't want to do it alone."

Titan was also much lighter than other submersibles, he said. Vessels made out of titanium or steel "all weigh 25 or so tons and they're huge," Rush explained. "The sub we built out of carbon fiber only weighs a little over 10 tons, we have five people on it— three laypeople, a pilot and a researcher—and it's still relatively small, which means it can go faster."

And, last but not least, Titan had a bathroom. Dives are 10 to 12 hours long, Rush noted, and on tinier subs "they give you a cup and a skirt that you wrap around your waist" when you have to go. "People would starve themselves the day before," he said. "It's a big fear. But because our sub is carbon fiber and we have so much space, we actually have a bathroom that is bigger than most private jets'. You can put up a little curtain and you have some privacy."

That being said, the toilet was still a plastic bottle and some Ziploc bags. The overall passenger compartment has been compared to the size of a minivan.

Ahead of what was supposed to be OceanGate's first Titanic dive with paying passengers in June 2019, Smithsonian reported that tickets were going to cost $105,129—the inflation-adjusted price for first-class passage on the Titanic—but had since gone up to $125,000 per person.

They didn't make that inaugural expedition until July 2021, OceanGate subsequently sharing on Twitter that they had set a record reaching the Titanic depths of 12,296 feet in a five-person carbon fiber submersible, making it in 2.5 hours and "landing directly in the least documented area of the debris field."

The Simpsons producer Mike Reiss made the trip in 2022. He recalled signing "a massive waiver that lists one way after another that you could die on the trip," telling the BBC in a June 20 interview, "They mention death three times on page one. So it's never far from your mind."

The waiver also notes that Titan is not approved or certified "by any regulatory body."

Who were the passengers aboard the OceanGate submersible Titan on June 18?

Rush, a 61-year-old father of two, was joined by Pakistani businessman Shahzada Dawood, 48, and his 19-year-old son Suleman Dawood, British billionaire Hamish Harding, 58, and former French navy diver Paul-Henri Nargeolet, 77, who like Harding was a member of The Explorers Club.

The company-described "mission specialists" paid $250,000 per person for an eight-day experience that included a number of dives.

Nargeolet was director of RMS Titanic Inc., the U.S. company that owns the salvage rights to the wreckage, and he had completed more than 35 dives to the site, including once on the Titan, according to the New York Times.

"For him to have died tragically in this way is almost impossible for me to process," Cameron told ABC.

Hamish, a father of two with wife Linda Harding, was chairman of the Dubai-based private jet brokerage Action Aviation and lived in the United Arab Emirates. The avid adventurer had visited the South Pole several times, reached the Mariana Trench (the deepest part of the ocean on Earth) and went to space in 2022 on Blue Origin's fifth human-crewed flight.

Shahzada Dawood, who hailed from one of Pakistan's richest families, lived in London with wife Christine and their daughter Alina. And apparently he was the one who wanted to see the Titanic while his son was reluctantly along for the ride for Father's Day. 

A family statement, per the BBC, said Suleman was a "big fan of science fiction literature and learning new things." But the teen, a business student at Strathclyde University, told a relative he was "terrified" about the deep-sea excursion, his aunt Azmeh Dawood told NBC News. 

"I feel like I've been caught in a really bad film, with a countdown, but you didn't know what you're counting down to," Azmeh said. "I personally have found it kind of difficult to breathe thinking of them."

What happened to the Titan submersible?

The Titan began its 2.4-mile trip below the ocean's surface from the Canadian expedition ship the Polar Prince on the morning of June 18, about 435 miles south of St. John's, Newfoundland.

The control center lost contact with the sub roughly an hour and 45 minutes into the dive.

A joint search operation involving the U.S. Coast Guard, U.S. Navy, Canadian Coast Guard and a number of private vessels commenced, ultimately traversing thousands of miles of ocean as time ticked away, the Titan's four-day oxygen supply providing the harshest of deadlines for a successful rescue operation.

Crews used sonar devices to try and catch any sound and deployed a remotely operated vehicle to comb the depths of the North Atlantic. 

"We wouldn't be searching and putting all effort out there" if they didn't think there was a chance of recovery, USCG Capt. Jamie Frederick said on June 20.

But retired U.S. Navy submarine captain David Marquet put the Titan passengers' chances of survival at "about 1 percent."

"It's basically imagining a spacecraft disappeared on the far side of the moon," he told NPR's Morning Edition two days into the search. "A, you have to find it. B, you have to get to it. Even when you get to it...you still need to somehow get the people out of there to safety."

It was possible, he added, "but I think the families should prepare themselves for bad news."

On June 21, the Coast Guard advised that "underwater noises" had been detected, after which "ROV operations were relocated in an attempt to explore the origin of the noises."

"Those ROV searches have yielded negative results," the agency said, "but continue."

When did officials determine the Titan submersible had imploded?

Officials estimated that the 96-hour oxygen deadline passed at roughly 7:10 a.m. ET on June 22.

That afternoon, the Coast Guard announced that a robotic vehicle from the vessel Horizon Arctic had discovered the tail cone of the Titan, as well as other large pieces of debris "consistent with a catastrophic loss of the pressure chamber," about 1,600 feet away from the bow of the Titanic. 

But even before pieces of Titan were found on the ocean seabed, officials had reason to suspect the sub was lost.

The U.S. Navy said that acoustic sensors had likely detected an implosion just hours after the dive began four days prior, meaning some senior officials suspected they weren't searching for an intact vessel.

"While not definitive, this information was immediately shared with the Incident Commander to assist with the ongoing search and rescue mission," a senior Navy official said in a June 22 statement to the Washington Post. "This information was considered with the compilation of additional acoustic data provided by other partners and the decision was made to continue our mission as a search and rescue and make every effort to save the lives on board."

Experts told NBC News that the water pressure that crushed the sub was akin to the weight of the 10,000-ton wrought-iron Eiffel Tower, but the implosion would have been so quick, no one aboard would have had even a second to react.

"They would have known nothing," said University of Southampton professor Paul White, an expert in underwater acoustics and forces. "The minute this body of water hit them, they would have been dead."

What caused the implosion of the Titanic-bound sub?

Officials have not yet been able to pinpoint a reason for why the expedition turned deadly, and investigations into the cause of the implosion are ongoing.

Cameron raised the possibility that the carbon-fiber composite that the Titan was built with, making it lighter than any other sub doing comparable dives, proved to be its undoing.

The material has "no strength in compression," the filmmaker, whose numerous expeditions include a solo dive to Challenger Deep—the deepest point of the Mariana Trench—aboard the 24-foot sub Deepsea Challenger in 2012, told the New York Times. "It's not what it's designed for."

Cameron has now said in multiple interviews that the deep-submergence engineering community generally abides by the strictest of certifications and safety protocol. Which, he pointed out, was why nothing like this tragedy had happened before.

"We've never had an accident like this," he told the Times. "There've never been fatalities at this kind of depth and certainly no implosions."