When he was about 20 years old, he was taken to the Falkland Islands by Luis Vernet, to work as a gaucho. Conditions of employment caused discontent among Vernet's workers. They were paid with promissory notes which Matthew Brisbane, Vernet's deputy, devalued following the reduction in Vernet's fortunes. On 26 August 1833, five Indian convicts and three gauchos led by Rivero embarked on a killing spree which resulted in the deaths of Brisbane and the senior leaders of the settlement. Thomas Helsby, a clerk in the employ of Vernet, wrote an account of the murders.
At around ten in the morning, Helsby departed Brisbane's house to buy some oil from William Dickson, whom he found at the house of Antonio Wagner. Other people there included Daniel McKay and Joseph Douglas. On leaving, as he passed the house of Santiago Lopez, Helsby encountered the murderers. The gang was led by Rivero and comprised the gauchos José María Luna, Juan Brasido and the five Charrúa Indians Manuel Gonzales, Luciano Flores, Manuel Godoy, Felipe Salagar and Lattorre. They were armed with "muskets, pistols, swords, dirks and knives".
Alarmed, Helsby ran to Brisbane's house for aid, but he found it locked and could raise no response. He was informed by other residents that Brisbane had been killed, along with Juan Simon (the Capitan of the Gauchos). A third man, Don Ventura, had been left for dead, wounded in the throat by a musket, his head split and his hand almost severed by a sword, but he had since escaped by a back window and headed toward the house of Antonina Roxa. Helsby then heard two musket shots from the house of Antonio Wagner: Wagner and Dickson had been killed, witnessed by Joseph Douglas and Daniel McKay.
The gang then returned to Brisbane's house to find Ventura missing. After a brief search they found him. Ventura tried to flee, but was shot down. Helsby witnessed the murder and attempted his own escape, but was soon caught by Felipe Salagar, who was on horseback. Convinced he was about to be killed, he complied with their instructions, and was allowed to live.
|“||I was ordered by them into Captain Brisbane's house, and there first saw his body lying dead upon the floor, he appeared to have been making towards his pistols before he fell, and there was smile of contempt or disdain very strongly marked in his countenance. They dragged his body with a horse to a considerable distance, and plundered the house.||”|
The population of that time, mainly women and children, fled to the nearby Peat island, until rescued by the sealer Hopeful in October 1833, which then passed information about the murders to the British squadron at Rio de Janeiro.
In January 1834, the British ship HMS Challenger arrived in the islands, bringing Lt. Henry Smith, who set out to capture the murderers, who fled into the interior. The gang was sent for trial in London, but under the British Legal system could not be tried because the Crown Court did not have jurisdiction over the Falkland Islands at the time of the alleged offences. In the British colonial system, colonies had their own, distinct governments, finances, and judicial systems. Rivero was not tried and sentenced because the British local government and local judiciary had not yet been installed in 1834; these were created later, by the 1841 British Letters Patent. Subsequently, Rivero has acquired the status of a folk hero in Argentina, where he is portrayed as leading a rebellion against British rule. However, all five of the victims of the massacre were employees of Vernet. They were deported to Rio de Janeiro, and returned later to the zone of the Río de la Plata.
The circumstances of Rivero's death are unknown.
The initial British plans for the Falklands were based on the perpetuation of Vernet's settlement, backed by an annual visit by a warship. This was the standard practice of maintaining a settlement with the minimum of expense. Thus, there was no British presence in the islands at the time of the Port Louis murders. A direct result of the murders was the installation of a permanent British Government presence – Lt Henry Smith became the first British resident in January 1834. Subsequently, the permanent presence led to the decision in 1841 to form a permanent colony rather than a minor naval outpost.
In popular culture
Armando S. Fernández wrote in 2008 a historical novel about Rivero, called "El Gaucho Rivero y la conspiración para apoderarse de Malvinas".
In 2011 and 2012, starting at Tierra del Fuego Province, Argentine provinces with shores to the Atlantic ocean passed a bill that banned ships sailing under the British flag from docking in their ports. These laws were collectively known as Ley Gaucho Rivero, as originally named in Tierra del Fuego, after Antonio Rivero.
In 2015, a new banknote was issued by the Argentine government themed on the Falkland Islands. In the reverse, Antonio Rivero is depicted on a horse flying the flag of Argentina.
- Thomas Helsby. "Thomas Helsby's Account of the Port Louis Murders". Captain Onslow's report of the visit of HMS Clio to Port Louis in January 1833; Narrative by Port Louis settler Thomas Helsby. Wikisource. Retrieved 2010-09-04.
- "A Brief History of the Falkland Islands, Part 3 - Louis Vernet: The Great Entrepreneur". falklands.info. Archived from the original on 2010-04-01. Retrieved 2010-09-04.
- Mary Cawkell (2001). The History of the Falkland Islands. Anthony Nelson. p. 63. ISBN 978-0-904614-55-8. Retrieved 20 September 2012.
- Extract of Thomas Helsby's Account of the Port Louis Murders Falkland Islands Government Archives, Stanley.
- "British colonies". Hutchinson encyclopedia. Retrieved 2010-09-04.
- Karsten, Peter, Between Law and Custom, "High" and "Low" Legal Cultures in the Lands of the British Diaspora - The United States, Canada, Australia and New Zealand, 1600-1900
- Laurio H. Destéfani, The Malvinas, the South Georgias and the South Sandwich Islands, the conflict with Britain, Buenos Aires: Edipress, 1982. pp. 91-92. ISBN 950-01-6904-5
- Cawkell, 2001, p. 63
-  The reluctant colonization of the Falkland Islands,1833-1851 : a study of British Imperialism in the Southwest Atlantic, Shannon Warnick, Masters Thesis, University of Richmond, December 2008, p.55-58
- The British Reoccupation and Colonization of the Falkland Islands, or Malvinas, 1832-1843 Barry M. GoughAlbion: A Quarterly Journal Concerned with British Studies Vol. 22, No. 2 (Summer, 1990) , pp. 261-287, Published by: The North American Conference on British Studies, 
- "Publicaciones". La Gazeta Federal. Retrieved 11 July 2015.
- "British ships banned from docking in Buenos Aires". The Telegraph. 3 August 2012. Retrieved 10 July 2015.
- "Malvinas Islands/Gaucho Rivero 50-Peso bill to honor Argentine fallen soldiers". MercoPress. 2 April 2014. Retrieved 10 July 2015.
- Ware, Richard. "The Case of Antonio Rivero and Sovereignty over the Falkland Islands," The Historical Journal (1984) 27#4 pp. 961–967 in JSTOR
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