The arrest of the 26-year-old Olympic and Paralympic track star stunned a nation that holds him up as hero who triumphed over adversity to compete with able-bodied athletes at the highest levels of sport.
His girlfriend, model Reeva Steenkamp, was found shot dead in his plush Pretoria home in the early hours of Thursday, police said, announcing that they had opened a murder investigation.
Initial reports of the shooting suggested Pistorius may have mistaken Steenkamp for an intruder.
The evening edition of Johannesburg's Star newspaper plastered the case across its front page, with a banner headline: "Oscar arrested: Girlfriend killed".
A 9 mm pistol was recovered from the scene, and police said there had been previous incidents of "a domestic nature" at the residence, which sits in the middle of a heavily guarded gated complex in the northern outskirts of the South African capital.
Pistorius had initially been expected to appear in court on Thursday but the hearing was postponed to Friday, National Prosecuting Authority officials said. The court is due to open at 0700 GMT but it is not known when Pistorius will appear.
He is being held overnight at Pretoria's Boschkop police station after undergoing medical and forensic examinations, police said. Police have said they will oppose bail.
"He is doing well but very emotional" his lawyer, Kenny Oldwage, told SABC TV, but gave no further comment.
Police brigadier Denise Beukes said witnesses had been interviewed about the incident which happened in the early hours of the morning.
"We are talking about neighbours and people that heard things earlier in the evening and when the shooting took place," she said.
"When a person has been accused of a crime like murder they (the district surgeon) look at things like testing under the finger nails, taking a blood alcohol sample and all kinds of other test that are done. They are standard medical tests," Beukes said.
South Africa's M-Net cable TV channel immediately pulled adverts featuring Pistorius off air but most of his sponsors, including sports apparel group Nike, said they would not make any decisions until the police investigation is completed.
Pistorius's endorsements and sponsorships, which also include telecoms firm BT, sunglasses maker Oakley and French designer Thierry Mugler, are thought to be worth as much as $2 million a year.
Pistorius, who was born without a fibula in both legs, was the first double amputee to run in the Olympics and reached the 400-metres 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 questioned the legitimacy of Brazilian winner Alan Oliveira's prosthetic blades, but was quick to express regret for the comments.
South Africa has some of the world's highest rates of violent crime, and many home owners have weapons to defend themselves against intruders, although Pistorius's complex is surrounded by a three-metre high wall and electric fence.
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.
Steenkamp, a model and regular on the South African party circuit, was reported to have been dating Pistorius for a year, and there had been little to suggest their relationship was in trouble.
In the social pages of last weekend's Sunday Independent she described him as having "impeccable" taste.
"His gifts are always thoughtful," she was quoted as saying.
Some of her last Twitter postings indicated she was looking forward to celebrating Valentine's Day on Thursday with him.
"What do you have up your sleeve for your love tomorrow???" she posted.
However, Beukes said the police were aware of previous incidents at the house of a "domestic nature", and recent media interviews with Pistorius revealed he kept an assortment of weapons in his home.
"Cricket and baseball bats lay behind the door, a pistol by his bed and a machine gun by a window," the Daily Mail wrote in a profile published last year.
He was arrested in 2009 for assault after slamming a door on a woman and spent a night in police custody. Family and friends said it was just an accident and the charges were later dropped.
In last year's Paralympics he suffered his first loss over 200 metres in nine years. After the race he questioned the legitimacy of Brazilian winner Alan Oliveira's prosthetic blades, though he was quick to express his regret for the comments.
Neighbours expressed shock at the arrest of a "good guy".
"It is difficult to imagine an intruder entering this community, but we live in a country where intruders can get in wherever they want to," said one local resident, who did not want to be named.
"Oscar is a good guy, an upstanding neighbour, and if he is innocent I feel for this guy deeply," he said.