Colonists were very prone to writing detailed scripts of their daily lives. Not just their daily diary entry, they wrote reports, letters to other colonists, detailed communique to higher-ranking officials along with a plethora of other documents which are now a trail of evidence for historians and others to analyze. 

Below is an article penned by WA researcher, Dr Jeremy Marten's who is based at UWA. 

https://theconversation.com/new-research-shows-was-first-governor-condoned-killing-of-noongar-people-despite-proclaiming-all-equal-under-law-165871