Four Māori and 22 Europeans were killed in the first violent clash between Māori and Pākehā since the signing of the Treaty of Waitangi.
Nelson colonists were keen to occupy the Wairau Valley, where the New Zealand Company claimed to have purchased land. Ngāti Toa disagreed, obstructing surveyors and destroying their huts. The chief Te Rauparaha insisted on an investigation by William Spain, who was looking into pre-1840 land purchases. Instead, warrants were issued for the arrest of Te Rauparaha and his nephew Te Rangihaeata, and an armed but untrained posse set out from Nelson to detain them.
When the two groups met at Tuamarina, fighting broke out – possibly accidentally – and several people were killed on both sides. Many of the surviving Europeans were surrounded and forced to surrender. After Te Rangihaeata demanded utu for the death of his wife, Te Rongo, the prisoners were killed – most by Te Rangihaeata using his mere.
Pākehā fears of a Māori insurrection proved groundless. The incoming governor, Robert FitzRoy, enraged settlers by arguing that the Europeans had provoked Ngāti Toa.