Theo Mostert, corporate services manager at the South African high commission in Suva, Fiji, evaded prosecution after being recalled to South Africa.
His death is a blow for the family of 26-year-old Ashneel Singh who were determined to put political pressure on South Africa to waive Mostert's diplomatic immunity and have him extradited to stand trial in Fiji.
Department of International Relations and Cooperation spokesman Nelson Kgwete confirmed that Mostert died last week, but declined to disclose the cause of death.
Singh and his fiancée, Janice Jyotika Prasad, a radio presenter, were hit by a Mazda driven by Mostert while en route to watch an evening movie last October.
Prasad survived the impact and told the Fiji Sun last month: "The person who is responsible for Ashneel’s death destroyed both our lives. Ashneel was one person who turned my frowns into smiles and I still love him and always will.”
Former Fiji police commissioner Ben Groenewald told the Sunday Times last month that police officers suspected Mostert was drunk and had subjected him to a breathalyser test.
Groenewald said there was a prescribed minimum sentence of five years' imprisonment in Fiji for killing a person through reckless driving or driving under the influence.
The case caused an outcry that prompted the Fijian government to ask South Africa to waive diplomatic immunity in order to prosecute Mostert. Talks between both countries were continuing at the time of his death.
Singh's family have made repeated calls to officials at the South African high commission in Suva for some form of financial assistance. Ashneel was the family breadwinner.
Booysen Dombo, first secretary at the South African embassy in Oslo, Norway, also avoided prosecution, citing diplomatic immunity, after crashing into a car in the capital city on January 3.
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