Police on Thursday said they had opened a murder case after a 30-year-old woman was found shot dead at the scene in the upmarket Silver Woods gated community on the outskirts of the capital.
Police spokesperson Katlego Mogale said a 9mm pistol had been found at the scene and a 26-year-old man was taken into custody. In South Africa police does not identify suspects until they are charged in court.
"There are witnesses and they have been interviewed this morning. We are talking to neighbours and people that heard things earlier in the evening and when the shooting took place," police Brigadier Denise Beukes told reporters outside the residential complex in Pretoria.
"At this stage he is on his way to a district surgeon for medical examination and will be appearing at the Pretoria Magistrate's Court at 2pm this afternoon."
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. The radio had said before the murder charge that he might have mistaken her for a burglar.
According to media, police are set to oppose bail for "Blade Runner" – his nickname for his racing prosthetics.
According to News24, Beukes has confirmed that there have "previously been allegations of a domestic nature at Mr Pistorius's home".
'His gifts are thoughtful'
Reeva Steenkamp was reported to have been dating Pistorius for a year. 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.
"We are all devastated. Her family is in shock," Steenkamp's agent, Sarita Tomlinson, said, in tears over the incident, which happened in the early hours of the morning.
"They did have a good relationship," she said. "Nobody actually knows what happened."
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 400m semifinals 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, though he was quick to express his 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.
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's lavish home is in the heart of a large estate surrounded by a 3-metre-high stone wall topped by an electric wire fence.
"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 of the residents, 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.
Pistorius did not answer his mobile phone on Thursday. His South African agent told Reuters he had not spoken to Pistorius but his lawyers were with him.
He is sponsored by British telecommunications firm BT, sunglasses maker Oakley, sports apparel maker Nike and French designer Thierry Mugler.
"We are shocked by this terrible, tragic news. We await the outcome of the South African police investigation," a BT spokesperson said before Pistorius was charged.
A Nike spokesperson in London said before hearing of the murder charge that the company was "saddened by the news, but we have no further comment to make at this stage". – Reuters