I don't know where you get this from, probably from watching too much American T.V where they "sue your ass off", you have to remember we live in AUSTRALIA. It is now very hard in Australia to sue someone civilly, there is also safeguards in place to protect what is known as 'Samaritan's' who are attempting to do the right thing, but may inadvertently cause injury/ death. Additional information can be found by searching for public liability restrictions.

Good on you for stopping and helping him. As all have said if you leave the scene of an accident without exchanging details (that is if you are directly involved in e.g you crashed into him) then you are committing a criminal offence.

Though you cannot be charged with anything if you simply sit there and watch the man bleed out on the road, and anything minor they could think of if they did want to charge you with could easily be defeated in court.