A missing submersible imploded near the wreckage of the Titanic, the U.S. Coast Guard said Thursday, killing all five people on board. Coast Guard officials say debris found during a dayslong search for the Titan "is consistent with a catastrophic implosion of the vessel." Video above: Former Navy submersible pilot on what could cause cause 'catastrophic implosion'Here's a look at what we know about what led up to this discovery: When did the submersible go missing? The craft submerged Sunday morning, and its support vessel lost contact with it about an hour and 45 minutes later, according to the Coast Guard.The vessel was reported overdue about 435 miles south of St. John’s, Newfoundland, according to Canada’s Joint Rescue Coordination Centre in Halifax, Nova Scotia.The Titan was launched from an icebreaker that was hired by OceanGate and formerly operated by the Canadian Coast Guard. The ship has ferried dozens of people and the submersible craft to the North Atlantic wreck site, where the Titan has made multiple dives.What search efforts were made? The Titan was estimated to have about a four-day supply of breathable air when it launched Sunday morning in the North Atlantic — but experts have emphasized that was an imprecise approximation to begin with and would have been extended if the passengers took measures to conserve breathable air. Rescuers rushed ships, planes and other equipment to the site of the disappearance. On Thursday, the U.S. Coast Guard said an undersea robot sent by a Canadian ship had reached the sea floor, while a French research institute said a deep-diving robot with cameras, lights and arms also joined the operation.When did the implosion occur?Rear Adm. John Mauger, of the First Coast Guard District, said it was too soon to say whether the implosion happened at the time of the submersible's last communication on Sunday. “We had listening devices in the water throughout and did not hear any signs of catastrophic failure from those,” he said.A senior military official said Thursday that a U.S. Navy acoustic system detected an “anomaly” Sunday that was likely the Titan’s fatal implosion.The senior military official said that the Navy went back and analyzed its acoustic data after the Titan was reported missing. That anomaly was “consistent with an implosion or explosion in the general vicinity of where the Titan submersible was operating when communications were lost,” the official said.The official spoke on condition of anonymity to discuss a sensitive acoustic detection system.The Navy passed on the information to the Coast Guard, which continued its search because the Navy did not consider the data to be definitive. If the submersible imploded, what were those banging sounds rescue crews heard earlier this week? Authorities were hoping underwater sounds detected Tuesday and Wednesday might help narrow their search, whose coverage area had been expanded to thousands of miles — twice the size of Connecticut and in waters 2 1/2 miles deep.But the Coast Guard indicated Thursday that the sounds were likely generated by something other than the Titan.“There doesn’t appear to be any connection between the noises and the location (of the debris) on the seafloor,” Mauger said.Who were the five people on board?A renowned Titanic expert, a world-record-holding adventurer, two members of one of Pakistan's wealthiest families and the CEO of the company leading an expedition to the world's most famous shipwreck all lost their lives on the submersible expedition. They are:Stockton Rush founded OceanGate Inc. in 2009 to provide crewed submersibles for undersea researchers and explorers, according to the company's website. Rush was the Titan's pilot, said company spokesperson Andrew Von Kerens.Hamish Harding, a British businessman, lived in Dubai in the United Arab Emirates. Action Aviation, an aircraft brokering company for which Harding serves as chairman, said he was one of the mission specialists, who paid to go on the expedition. Harding was an avid adventurer, having traveled to space on board the Blue Origin flight last year, and to the Challenger Deep in the Pacific Ocean, believed to be the deepest point in the world.Shahzada and Suleman Dawood, who are father and son, are members of one of Pakistan's most prominent families. Their family said in a statement that they were both aboard the vessel. The business family runs some of the largest corporations in the country, with a portfolio spanning energy, petrochemicals, fertilizers, IT and food and agriculture.Paul-Henri Nargeolet is a former French navy officer who is considered a Titanic expert after making multiple trips to the wreckage over several decades. The diver has decades of experience exploring the Titanic. He served as the director of underwater research at RMS Titanic Inc., the company that has exclusive rights to salvage artifacts from the ship.What challenges arose during the search? Dr. Rob Larter, a marine geophysicist with the British Antarctic Survey, emphasized the difficulty of finding something the size of the submersible, which is about 22 feet long and 9 feet high.“You’re talking about totally dark environments," in which an object several dozen feet away can be missed, he said. "It’s just a needle in a haystack situation unless you’ve got a pretty precise location.”Nick Rotker, who leads underwater research for the nonprofit research and development company MITRE, said the difficulty in searching for the Titan underscored the U.S.'s need for more underwater robots and remotely operated underwater vehicles.“The issue is, we don’t have a lot of capability or systems that can go to the depth this vessel was going to,” Rotker said.Nicolai Roterman, a deep-sea ecologist and lecturer in marine biology at the University of Portsmouth, England, said the disappearance of the Titan highlights the dangers and unknowns of deep-sea tourism.“Even the most reliable technology can fail, and therefore accidents will happen. With the growth in deep-sea tourism, we must expect more incidents like this.”What's next? The Coast Guard will continue searching near the Titanic for more clues about what happened to the Titan. Efforts to recover the submersible and the remains of the five men who died will also continue, Mauger said.Officials say there isn’t a timeframe for when they will call off the massive international search. Mauger said that the prospect of finding or recovering remains was unknown.The Associated Press and CNN contributed to this story.