Bystander apathy
As an Aussie who has lived in the States for over a decade, I found the premise underpinning the storyline to 'Jindabyne', that four guys would be so apathetic and self-involved in such tragic circumstances, hard to credit.
It's a movie based on an American author's short story, set in America, about a particular malaise, bystander apathy, somewhat peculiar to the U.S.A., so much so that they've had to legislate against it. Some could argue that lawyers, and the climate of rampant and opportunistic litigation that they've made so prevalent in the States, may be responsible for the modern day attitude of people not wanting to 'get involved', of shying away from their moral responsibilities and simply looking out for number one. Whatever the arguments, the fact remains that the prevailing climate of human disengagement - in America - is at the core of the author's story, and it doesn't translate well to Australia, because that kind of climate doesn't really exist on such a level in the country. I could perhaps imagine one individual, at odds with his fellow citizens, acting in such a heartless manner, but not a group of them - unless of course they were blind drunk from the 26 cases of beer they would have ferried in and too catatonic to do anything other than roll over for the sake of vomiting!
No doubt the comment will earn the ire of a few American readers, but hey, I've lived in your country for over a decade and only have to go out for a drive to see how horrendously self-involved people here are. Getting a green light at an intersection is an invitation to commit suicide by heading out in the path of the obligatory red light runners for whom consideration of human life is of scant regard when measured against the inconvenience of being held up for a minute or so on their all-important and triumphant march through their own lives.