Wiremu Hīroki is thought to have been born in the mid 1850s, at Waitōtara in southern Taranaki. As a youth he lived with Ngāti Pourua, a major hapū of Ngā Rauru, at Papatupu, near Waitōtara. Those who knew him were either uncertain of his descent or wanted to disown him as an embarrassment. Some Māori said he was of Waikato origin; Hīroki told a Taranaki Herald journalist in 1878 that his parents were of Ngāti Maniapoto and Ngāti Ruanui. He may also have had Ngā Rauru connections.
Hīroki's low rank and youth made him a follower, not a leader. He fought the enemies of his chiefs. When Ngā Rauru were allied to Tītokowaru he fought for him against the government, probably under the Ngā Rauru chief Kereopa. In early 1870, however, he was one of a force led by Tōpia Tūroa and Te Keepa Te Rangihiwinui (Major Kemp) which reinforced Colonel Thomas McDonnell's Tokaanu-based Armed Constabulary force in pursuit of Te Kooti. On the morning of 25 January 1870, while camping in thick fog after taking Tāpapa pā, three Ngā Rauru, including Hīroki, were sent to fetch firewood. The three stumbled on Te Kooti's party. One was killed, but Hīroki protected his companion and shot two of the enemy.
After the wars Hīroki lived at Papatupu, sometimes working for the Waitōtara settler Francis Williamson. He was short, with a round head, full dark eyes, and a large mouth 'drooping at the corners'. His domestic life is something of a mystery. While a follower of Tītokowaru, Hīroki had been married to a daughter of Rangirahi of Ōkaiawa, but she was taken from him. By 1878 he was said to be married to Herera, whose father was Kātene of Pipiriki. In 1882 Hīroki wrote to his wife, addressing her as Whaka Pāhui. They had a son and a daughter.
In early 1878 government surveyors began to survey the Moumāhaki block, land in which Hīroki claimed an interest and on which he ran branded pigs. Trouble immediately arose over the killing of pigs by surveyors. In spite of the advice of his kin to leave the land to the government and go to Parihaka (the village of the pacifist leaders Tohu and Te Whiti-o-Rongomai), Hīroki was determined to hold on to it. He later claimed to have met John Sheehan, the native minister, in January at Māhaki (Sheehan refused to become involved with the matter), and to have told Murdoch McLean, a surveyors' labourer, that no Europeans were to go on his land. He had also warned Charles Brown, the civil commissioner, and later McLean, that he would kill any surveyors who did so. Despite these claims, many Europeans believed that Hīroki's differences with the McLean family sprang from a private quarrel.
About the beginning of September 1878 Hīroki complained to Francis Williamson about the killing of his pigs by the surveyors. Murdoch McLean, Williamson later testified, lied in denying that he had killed Hīroki's pigs. Williamson advised Hīroki to summons the surveyors, but Hīroki replied that 'he was only one and could not prove it and would get no satisfaction…he would do some evil to them.' Williamson cautioned the survey party about his threats.
Hīroki gave several accounts of the events of 19 September 1878 – the killing of a member of the survey party – for which he was to stand trial. In the first, given in November, he said the land being surveyed belonged to his father and he objected to its being sold. On the day in question he intended to shoot two Māori who, he considered, had given the land over to the Europeans. Fetching his gun, he saw a European with a gun cocked and aimed at him, so he fired. In another account, given to Archdeacon Henry Govett in May 1882 and corroborated by his last account on 6 June, he said that the real culprit was Tamanui, a Ngāti Pourua chief, whose idea it was to kill the surveyors, and who was being protected because of his rank. Tamanui and Hīroki had gone together to the surveyors' camp. The camp's cook, John McLean, brother of Murdoch, had fired at Hīroki. Hīroki took McLean's gun, and both he and Tamanui fired at McLean as he fled. Tamanui had then looted one of the tents, dividing the spoils with Hīroki, and suggested shooting the horses. Hīroki replied, 'it was not the horse that was surveying my land'.
Hīroki went home to Papatupu and told his people what had happened. He then set out on foot to take refuge at Parihaka, nearly 100 miles to the north-east. In the next month rumours abounded. Settlers feared that the murder of McLean presaged a general uprising against the survey of the Waimate plain. Suspicion had immediately fallen on Hīroki. Numerous sightings were reported, and it was rumoured that he was travelling into the King Country or Taupō via the upper Whanganui River. Posses comprising both Māori (including Tamanui) and Pākehā searched for him, and telegrams flew between the government and former 'rebel' chiefs, full of mutual reassurances. Hīroki's chiefs and kin, fearing further trouble with the government, disowned him and blackened his reputation.
Hīroki was sighted, fired at and wounded on 6 October near Kaūpokonui. It was now certain that his intention was to take refuge at Parihaka. A posse, led by the interpreter William Williams and the Ngā Rauru chief Aperahama Tama-i-parea, broke into Parihaka during the next monthly meeting, demanded that Hīroki be handed over to them and began to search the houses. They were peremptorily ordered to leave because, Tītokowaru explained to the native minister, they had not asked permission to search or in any way conformed to proper etiquette when approaching Parihaka.
If there were doubts about the political nature of McLean's murder, there were none about Te Whiti's protection of Hīroki at Parihaka. The interpreter R. S. Thompson frequently advised the government to make Hīroki the prime issue. He wrote: 'it is more than probable that Te Whiti would refuse to give him up and then we should have to take him and whilst doing so would so cripple Te Whiti that he would never be able to raise the issue of the confiscation again.' By February 1880 John Bryce, the minister for native affairs, was hesitating to take Thompson's advice only because of the political consequences of failure.
Hīroki's position at Parihaka was equivocal. Te Whiti told Charles Brown in April 1879 that he would have had nothing to say if Hīroki had been killed on his way north. At Parihaka Hīroki was treated as he had always been – as a man of no rank; he helped with the cooking. In 1880 the west coast commissioners, William Fox and Francis Dillon Bell, argued that Te Whiti's protection of Hīroki was no reason to refuse to return the Parihaka block. But Bryce used Hīroki's sanctuary with Te Whiti to justify the detention without trial of Te Whiti's ploughmen. When Bryce resigned in January 1881 because the government refused to back his aggressive native policy, he again made Hīroki the issue.
On 5 November 1881 Bryce, reappointed minister for native affairs, led a force of over 1,500 into Parihaka. Hīroki stepped forward when his name was called, was handcuffed and marched under escort to Pungarehu. During his captivity he was kept separately and treated more harshly than Te Whiti and Tohu, who were regarded as political prisoners. On 12 November Te Whiti, Tohu and Hīroki were transferred to New Plymouth gaol. Hīroki's trial began on 3 May 1882. Among those who testified was Tamanui. Hīroki was found guilty of murder and sentenced to death. He caused a slight stir after his trial when he claimed that Tamanui was his accomplice, but after brief investigation this claim was officially dismissed. At 8 a.m. on 8 June 1882, Wiremu Hīroki was hanged.