A historical investigation of the Deeban rockfall mystery claims hundreds of Dhawaral people who lived in the Bundeena area died in a collapased cave.
The claims made by Ian Wilson are based on historical newspaper clippings and surmises two possible explanations for what happened.
The first explanation claims a rock had crushed more than a hundred Aboriginal people who had been camping in the cave beneath as a result of a lightning strike.
The second explanation is less clear but that a site containing a large quantity of Aboriginal cultural items under a rock shelf had been destroyed by Harry Simpson.
For more details of the Deeban rockfall mystery see Colonisation of a Tharawal story: Bringing out the truth of a tragedy