South African Paralympic athlete Oscar Pistorius has reportedly been arrested over the fatal shooting of his girlfriend at his home in Pretoria.
Police said a 26-year-old man, who they have not named, is in custody and a case of murder is being investigated.
The precise circumstances surrounding the incident are unclear. Reports say he may have mistaken her for a burglar.
Pistorius, 26, is known as the "blade runner", and was the first double amputee to run in the Olympics, the BBC reports.
The incident is said to have taken place between 4am and 5am (local time) on Thursday.
A police statement said that a 30-year-old woman was "fatally wounded" at a home in the Silverlakes complex in the Boschkop area of the capital.
The woman had been wounded in her head and upper body. Paramedics were at the house when police arrived, but she died at the scene. A 9mm pistol has been recovered.
Some local media are suggesting that Pistorius's girlfriend was sneaking in to surprise him for Valentine's Day. She is being named as 30-year-old model Reeva Steenkamp.
South Africa has among the highest rates of crime in the world and many residents keep weapons to protect themselves against intruders, but it does have a careful vetting process, the BBC reports.
Pistorius races wearing carbon fibre prosthetic blades after he was born without a fibula in both legs and reached the 400m semi-finals in the London Games.
For years he dominated in his category at successive Paralympic Games after winning medals at the Athens Olympics in 2004.