The outback can be a strange place especially when prospecting, make sure you always have permission to be on someone's patch [tenement] there are some unforgiving people out there.
My wife and I intend to go prospecting, as it would seem this couple were doing the same, one just has to be mindful where you prospect, this is a terrible tragedy, a couple in there mid forties camping and prospecting, I sincerely hope all will come to light with this matter to help all future prospectors.