Robert Brown|What we know about the 5 men who were aboard the wrecked Titan sub

The Robert Brownfive people who have been missing since going on a deep sea dive destined for the Titanic shipwreck are believe to have died, officials said Thursday.

"These men were true explorers who shared a distinct spirit of adventure, and a deep passion for exploring and protecting the world's oceans," OceanGate, the company that developed the submersible, said in a statement. "Our hearts are with these five souls and every member of their families during this tragic time."

The passengers included British businessman Hamish Harding, Pakistani investor Shahzada Dawood and his son Suleman, French diver Paul-Henri Nargeolet and OceanGate CEO Stockton Rush.

Here's what we know about them.

Hamish Harding

Harding was the chairman of Action Aviation, an aviation sales and consulting company.

Retired NASA astronaut Terry Virts told NPR his friend Harding "is an explorer by nature."

Harding broke the Guinness world record for the fastest flight around both the Earth's poles in 2019, in which Virts was a crew member. Harding has additionally broken Guinness world records for the longest duration at a full ocean depth by a crewed vessel and the longest distance traveled along the deepest part of the ocean.

Shahzada Dawood

Dawood was the vice chairman of Engro, a Pakistani energy investment company, and the Dawood Hercules Corp., an investment and holdings firm. He had expertise in mergers and acquisitions in companies across industries, such as textiles, fertilizers, foods and energy.

Additionally, he served on various boards, including the SETI Institute, a NASA-funded nonprofit dedicated to extraterrestrial research, and Prince Charles' charity, Prince's Trust International.

Dawood obtained an undergraduate law degree from Buckingham University in the U.K. and a master's of science in global textile marketing from Philadelphia University (now known as Thomas Jefferson University).

He is survived by his wife, Christine, and his daughter, Alina.

Suleman Dawood

The 19-year-old Suleman, a college student, was the son of Shahzada Dawood.

He had recently completed his first year as a business major at the University of Strathclyde in Glasgow, Scotland.

Stockton Rush

Rush, a British businessman, founded OceanGate in 2009 and served as the organization's CEO, overseeing the development of submersibles that would be able to travel up to 20,000 feet below the ocean's surface.

"Taking an early lead in an emerging market, Stockton recognized that private industry funding and utilization of modern materials could have a major impact on our ability to explore the deep oceans while significantly lowering the cost of discovery," the OceanGate website says.

In 1981, Rush became the youngest jet transport rated pilot in the world at the time at 19, flying to destinations, such as Cairo, Mumbai and Zurich, according to his biography.

He received a bachelor's degree in aerospace engineering from Princeton University and a business master's degree from UC Berkeley. In 1989, he developed his own experimental aircraft, which he had flown before.

He additionally served on boards and development teams for companies making sonar systems, software and remote controls, as well as at The Museum of Flight in Seattle.

Paul-Henri Nargeolet

Nargeolet, known as "Mr. Titanic" for his expertise of the ship, spent 22 years in the French navy, where he was eventually ranked commander. He retired from the navy in 1986 and oversaw two deep sea submersibles at the French Institute for Research and Exploitation of the Sea. While there, he led the first recovery dive to the Titanic wreckage in 1987, according to his biography.

He was the director of underwater research for RMS Titanic Inc., a company dedicated to preserving the history of the Titanic, and the E/M Group, a company that provides exhibitions and other entertainment.

He completed 37 dives in a submersible to the Titanic shipwreck over the course of his career, and supervised the retrieval of 5,000 of its artifacts, including a 20-ton section of the hull.

Nargeolet was born in Chamonix, France, but lived in Africa for 13 years with his family before returning to France at age 16.