Samuel Wanjiru was born in Nyahururu, Laikipia County, a town in the Rift Valley, about 150 kilometres (93 mi) northwest of the capital, Nairobi.

[6] After graduating in 2005, he joined the Toyota Kyūshū athletics team, coached by 1992 Olympic marathon silver medalist Koichi Morishita.

This was preceded two weeks earlier by a bettering of the 10,000 m world junior record by a margin of almost 23 seconds in the IAAF Golden League Van Damme Memorial Race on 26 August.

[19] The wins in London and Chicago helped him reach the top of the World Marathon Majors rankings for 2009, earning him a jackpot of US$500,000.

[21] He chose to run at the 2010 Chicago Marathon in October, but a stomach virus before the race had harmed his preparations and he entered the competition with the lesser aim of reaching the top three.

Tsegaye Kebede took the opportunity to forge a lead, but Wanjiru (despite a lack of peak physical form) persevered with the pace and caught up with the Ethiopian.

He had previously married Triza Njeri in a traditional ceremony and had two children, although Wanjiru and Wacera's marriage was legally binding.

[25] In December 2010, Wanjiru was arrested by Kenyan police at his house in Nyahururu and charged with threatening to kill his wife and illegally possessing an AK-47 rifle.

Wanjiru appeared to have suffered internal injuries after the fall and was confirmed dead by doctors at a nearby hospital after attempts to revive him failed.

[2] Police were unsure if Wanjiru intended suicide or jumped out of rage, and investigated the circumstances related to Njeri and his female companion that led to his death.

[34][35][36][25] His mother claimed at an inquest into his death that her son was murdered by six men who had conspired with his wife Trizah Njeri.