He had dived into the water to give the woman her turn on the board when he was attacked, O'Connell said.
"There's just a period of time when conditions are such that it maybe causes attacks to be more frequent".
"CPR was ongoing for a very long time and every solid effort was made to save that man's life", O'Connell said.
Police said Tuesday that they have not publicly identified the man as they were still working to contact his next of kin. "It's just - the injuries were so severe", he added.
One of the rescuers, Ben McCauely, who also was involved in the previous two incidents, said it felt like "deja vu" but worse.
"Definitely one of the more hard ones for everyone involved", McCauley said.
"We are deeply saddened by the tragic loss of Dr Daniel Christidis who was a research fellow with Austin Health".
Marine biologist Blake Chapman says it's hard to say what has changed and whether the three attacks indicate an increase in shark activity - but he believes more research should be conducted to find out.
"Our thoughts are with his family during this extremely hard time. We simply do not know why this is occurring and what is responsible for it".
The victims were 12-year-old Melbourne girl Hannah Papps, who suffered a "significant leg injury" during the attack, and Tasmanian tourist 46-year-old Justine Barwick, who suffered severe injuries to her right thigh and had to undergo reconstructive surgery.
After Monday's attack, a local politician asked the Queensland state government to install permanent drum lines around Cid Harbour, like hundreds of other places along the eastern coast line.
Meanwhile, Fisheries Minister Mark Furner issued a stern warning.
Tourism Whitsundays CEO Natassia Wheeler said they supported all efforts to inform visitors about the dangers of sharks in the area.
Signs will be installed by this weekend telling people no one should swim in Cid Harbour under any circumstances.
Australia ranked behind only the United States in the number of unprovoked shark encounters with humans in 2017, according to the University of Florida's International Shark Attack File.
Tourism Whitsundays chief executive Peter O'Reilly said at the time that the Trumbull attack was the first in the islands in 13 years and only the third ever recorded.
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