Thomas Peel organised and lead a consortium of the first British settlers to Western Australia. He was a leader of the colonial militia that participated in Pinjarra massacre in 1834, which saw 70-80 of the Aboriginal Binjareb people killed. He was a second cousin of two-times British Prime Minister Sir Robert Peel.

The Pinjarra massacre, also known as the Battle of Pinjarra, occurred on 28 October 1834 in Pinjarra, Western Australia when a group of Binjareb Noongar people were attacked by a detachment of 25 soldiers, police, and settlers led by Governor James Stirling. According to Stirling, "about 60 or 70" of the Binjareb people were present at the camp and John Roe, who also participated, estimated about 70–80. This roughly agrees with an estimate of 70 by an unidentified eyewitness. The attack at Pinjarra was in response to sustained aggression by the Binjarebs, including robberies and murder of settlers and members of other Nyungar tribes.