R.L Ginibi wrote in this article:

Offences regarded as unlawful included the unauthorised killing of a person, sacrilege, incest, adultery, theft, unauthorised assault, insult and neglect of kinship obligations. Punishments could range from making compensation over an agreed period of time to having to face a squad of spearmen, with only a shield and that person's ability to protect himself.

J.L. Kohen wrote in this article about an aboriginal warrior named Pemulwuy:

Raids were made for food, particularly corn, or as 'payback' for atrocities: Collins suggested that most of the attacks were the result of the settlers' 'own misconduct', including the kidnapping of Aboriginal children.

The same type of thing happened in other instances of White/Aboriginal contact.