A former OceanGate advisor said the Titanic submersible tried to reach the surface before it imploded, indicating those on board knew something had gone wrong

• A former OceanGate advisor said the Titan sub dropped its weights before it imploded on June 18.
• Rob McCallum told The New Yorker that it tried to ascend before losing contact with its mother ship.

A former OceanGate advisor said the Titan submersible dropped its ballast and tried to ascend moments before going missing, likely meaning that the five people inside were already aborting the dive when it imploded.

Rob McCallum, an expedition consultant who previously gave OceanGate advice on marketing and logistics, told The New Yorker that he received early reports about the Titan's fateful final dive.

"The report that I got immediately after the event — long before they were overdue — was that the sub was approaching thirty-five hundred meters," he told the New Yorker's Ben Taub.

McCallum said the submersible had "dropped weights," which meant the dive was aborted, and then lost communication with its mother ship.

McCallum is the cofounder of the adventure-expedition company EYOS Expeditions. He's previously led dives to the Titanic's shipwreck and other deep-sea spots. But he used submarines designed to reach depths of 19,000 feet and a submersible that, unlike OceanGate's, was approved to reach extreme depths by the marine-classification society DNV.

He was in regular contact with OceanGate CEO Stockton Rush at one point and visited OceanGate's workshop, per the New Yorker. McCallum is at least the second person to publicly state that the Titan likely tried to ascend before it imploded.

James Cameron, a deep-sea expert who directed the "Titanic," also told ABC News on June 24 that he heard from "inside the community" that the Titan had dropped its weights and that those on board were "trying to manage an emergency."

The vessel lost contact with its mother ship on June 18, about 1 ½ hours into its journey carrying five people some 13,000 feet underwater to the shipwreck of the Titanic.

At such depths, the Titan likely imploded with so much force that those inside were killed instantly, with no time to realize the hull had collapsed.

Authorities are still investigating the implosion, and it's currently unclear whether the five passengers were aware of the impending danger or had advance warning of hull failure.

But Cameron's and McCallum's accounts of the dive timeline suggest that at least one person on board had — for reasons still unknown — discovered beforehand that something went wrong and chose to abort the journey.

Rush was piloting the submersible at the time, and he was likely in charge of the dive.

OceanGate previously aborted the Titan's dives when the submersible lost one of its propulsion systems and another time when several floats became detached from the vessel. The company has aborted more of the Titan's dives than it has completed, per The New York Times.

Former passengers said the Titan regularly ran into issues with its battery and ballast system.

Photos taken on Wednesday appear to show authorities unloading debris from the Titan submersible at the Canadian Coast Guard pier in St. John's, Newfoundland.

OceanGate did not immediately respond to a request for comment sent outside regular business hours.