South African Olympic and Paralympic track star Oscar Pistorius, known as the "Blade Runner" for his racing prosthetics, was arrested on Thursday after his girlfriend was shot dead at his home in Pretoria.
Police said they had opened a murder case after a 30-year-old woman was found dead at the scene in the upmarket Silverlakes gated community on the outskirts of the capital.
"We found a 9 mm pistol at the scene. A 26-year-old man was taken into custody," police spokesperson Katlego Mogale said.
In South Africa police do not identify suspects until they are charged in court. Johannesburg's Talk Radio 702 said Pistorius was believed to have shot his girlfriend, a model, in the head and arm, although the circumstances were unclear.
He may have mistaken her for a burglar, the radio report said. Reeva Steenkamp was reported to have been dating Pistorius for a year. In the social pages of last weekend's Sunday Independent, she described Pistorius as having "impeccable" taste.
"His gifts are always thoughtful," she was quoted as saying.
Pistorius, who races wearing carbon fibre prosthetic blades after he was born without a fibula in both legs, was the first double amputee to run in the Olympics and reached the 400 metre semi-finals in London 2012.
In last year's Paralympics he suffered his first loss over 200 metres in nine years. After the race he sullied his media darling persona somewhat by questioning the legitimacy of Brazilian winner Alan Oliveira's prosthetic blades.
The comments sparked controversy though Pistorius was quick to express his regret. South Africa has some of the world's highest rates of violent crime and many home owners have weapons to defend themselves against intruders.
In 2004, Springbok rugby player Rudi Visagie shot dead his 19-year-old daughter after he mistakenly thought she was a robber trying to steal his car in the middle of the night. Pistorius did not answer his mobile phone on hursday. His agent told Reuters he had not spoken to Pistorius but his lawyers were with him.