South African Olympic and Paralympic athlete Oscar Pistorius is facing a murder charge after his girlfriend was shot and killed at his Pretoria home.
His arrest over the death of model Reeva Steenkamp has stunned the country where he is considered a national hero.
The 26-year-old is due to appear in court on Friday.
Mr Pistorius made history in London last year when he became the first double-amputee track athlete to compete in the Olympic Games.
He is known as the "blade runner" because of the carbon fibre prosthetic blades he races in. He was born without a fibula in both legs and had his legs amputated below the knee before his first birthday.
Police were called to his home in the upmarket Silver Woods gated compound on the outskirts of South Africa's administrative capital in the early hours of Thursday morning.
They found paramedics treating a 29-year-old woman with four gunshot wounds to the head and upper body. She died at the scene, and officers recovered a 9mm pistol.
Early reports suggested Mr Pistorius might have mistaken his girlfriend for an intruder.
Police say neighbours heard screaming and shouting around the time of the shooting, and that they had been called to investigate incidents of a domestic nature at the same house in the past.
They also said that they would oppose any bail application.
Hours later, after being questioned by police, Mr Pistorius left a police station accompanied by officers, his face mostly covered by the hood of a grey jacket.
His court hearing was originally scheduled for Thursday afternoon but had been postponed until Friday to give forensic investigators time to carry out their work, said Medupe Simasiku, a spokesman for the prosecution.
Mr Pistorius's father, Henke, declined to comment but said: "We all pray for guidance and strength for Oscar and the lady's parents.''
Miss Steenkamp's publicist confirmed to the BBC that the 29-year-old model had died.
"Everyone who knew her is in tears. She was an absolute angel, the sweetest, sweetest human being, a kind human being," Sarit Tomlinson said.
'Day of love'
In her last Twitter messages, Miss Steenkamp had spoken about her excitement about Valentine's Day.
"What do you have up your sleeve for your love tomorrow?'' she tweeted. "It should be a day of love for everyone.''
Mr Pistorius dominated in his category at successive Paralympic Games, but in 2008 he won a legal battle over his blades - which critics said gave him an unfair advantage - with the International Association of Athletics Federations (IAAF) for the right to compete in able-bodied competitions.
He reached the 400m semi-finals in the London 2012 Olympics. At the Paralympics he won silver in the T44 200m, gold in the 4x100 relay and gold in the T44 400m, setting a Paralympic record.
He was named by Time Magazine last year as one of the world's 100 most influential people.
In interviews, he had spoken about his enjoyment of target shooting with his pistol, and an online advertisement featuring him for Nike read: "I am a bullet in the chamber."
Mr Pistorius's former coach, Andrea Giannini, spoke out in favour of the athlete following his arrest.
"No matter how bad the situation was, Oscar always stayed calm and positive,'' he told the Associated Press news agency. "Whenever he was tired or nervous he was still extremely nice to people. I never saw him violent.''
South Africa has one of the highest rates of crime in the world and many residents keep weapons to protect themselves against intruders.
But gun ownership is strictly regulated and it is not easy to obtain a licence.
On Tuesday, a bill seeking to give police extra powers to arrest anyone carrying a dangerous weapon in public was tabled before parliament, following a spate of violent strikes and protests last year.