Henry Hawson died from the old-fashioned version of a car accident. That is, he died from an accident in his horse and cart, when his cart was upturned and he was pinned underneath it. In the old colonial days with no modern transport, communications or ambulance services, his body was not found for 24 hours. He was aged 57.
Here is an article on the accident in the SA Register, 1849 (retrieved from TROVE)