South African Paralympian Oscar Pistorius has reportedly shot and killed his girlfriend.
Police confirmed with South African media that they have opened a murder case against Pistorius.
According to Afrikaans publication Beeld, Pistorius, 26, shot his girlfriend around 4am (local time) on Thursday at his Pretoria security estate in Silver Lakes, South Africa.
She was hit four times, including in the head and arm. Paramedics declared her dead at the scene. Police took possession of a 9mm pistol.
Initial reports said Pistorius had mistaken her for a burglar, while others believed she may have actually been surprising him with a gift for Valentine's Day when the tragic incident took place.
The dead woman is believed to be model Reeva Steenkamp.
Pistorius was taken into custody and gave blood tests at a hospital.
He will appear in the Pretoria Magistrate's Court on Thursday 11pm (AEDT), and it is understood authorities will oppose bail.
Police spokesperson Katlego Mogale said statements were being taken from neighbours.
Athletics Australia Chief Executive Officer Dallas O’Brien released a statement on the shooting incident.
"Obviously we have been made aware of the tragic news story developing in South Africa around Oscar Pistorius and the reported shooting of his girlfriend," he said.
"Clearly, all the details around this incident are still coming to light, and for this reason we have no information at this time about how this effects Oscar’s plans."
Pistorius races wearing carbon fibre prosthetic blades after he was born without a fibula in both legs.
He was the first double amputee to run in the Olympics and reached the 400 semi-finals at the London Games in 2012.
South Africa has some of the world's highest rates of violent crime and some home-owners carry weapons to defend themselves against intruders.