Police said they had opened a murder investigation after a 30-year-old woman was found dead in the upmarket Silver Lakes gated community on the outskirts of the capital, where the Paralympic and Olympic runner lives.
"We found a 9mm pistol at the scene. A 26-year-old man was taken into custody," a police spokeswoman said.
Details about the incident remain unclear. There was speculation in the local media that Pistorius may have mistaken her for a burglar and the shooting could have been a result of a Valentine's Day surprise gone wrong. Local media suggested that Steenkamp may have been trying to surprise her boyfriend in his home on the heavily guarded compound and had been mistaken for an intruder. She was shot four times in the head and the arm.
"I can confirm that a woman has been fatally wounded in a shooting at Oscar Pistorius's house," said the police spokeswoman. "A 26-year-old man has been taken into custody," she said. "The incident happened at 3am. We received a call and attended the scene. The call did not come from the man in custody but from another person. Currently there is an inquiry into what happened."
There was a large police presence outside Pistorius's house and media descended on the estate where the shooting happened. Pistorius will appear in court later on Thursday. A police spokesman said the sprinter was distraught. "We can't comment on his emotional wellbeing, but he is traumatised after losing someone close to him," he said.
Steenkamp, 30, a well-known South African model, had been dating Pistorius since November last year and was due to appear in a reality TV show called Tropika Island of Treasure. The law graduate from Port Elizabeth gave an interview to the Sunday Times in South Africa last week where she described her boyfriend as "an impeccable man who always has her best interests at heart".
In the last 24 hours she was tweeting about her hopes for Valentine's Day, writing: "What do you have up your sleeve for your love tomorrow??? #getexcited #ValentinesDay." In one of her last tweets she responded to one follower who said she was going to make her husband a card with her children. Steenkamp wrote: "That sounds amazing! Wow that's what it's all about! It should be a day of love for everyone :) may it be blessed!"
Steenkamp's publicist Sarit Tomlinson told Sky News that she was a "talented bright young girl" whose star was rising. "She was the sweetest human being and an absolute angel on Earth," she said. "She was the kindest most unbelievable girl." She said Steenkamp and Pistorius had been together for a couple of months in "a healthy fabulous relationship".
On Steenkamp's Facebook page – where she described herself as "SA Model, FHM Cover Girl, Tropika Island of Treasure Celeb Contestant, Law Graduate, Ambassador" – tributes poured in. Sibi Tshego Sibanda wrote: "Heaven has gained an Angel. Rest in peace," and Elmarie Hattingh wrote: "Rest in Peace Reeva, May God be with the family and friends."
South Africa has some of the world's highest rates of violent crime and some homeowners carry weapons to defend themselves against intruders.
There were indications that Pistorius did have fears about his safety. In an interview with the Daily Mail before the London 2012 Games it was revealed he slept with a pistol next to his bed and kept a machine gun by a window. Pistorius had been arrested previously. In September 2009 he was arrested for assault after slamming a door on a woman. Family and friends at the time said it was an accident.
Pistorius, known as Blade Runner because of the carbon fibre prosthetic blades he wears to race, is the world's best-known Paralympic star. He was born without fibulas in both legs and had his legs amputated as an 11-month-old. He made history at London 2012 when he became the first double amputee to run in both the Olympics and Paralympics, running in the 400m and 4x400m relay at the Olympics. During and after the competition he regularly tweeted pictures of him and his girlfriend together.
The Johannesburg-born athlete won a legal battle over his blades with the International Association of Athletics Federations (IAAF) in 2008 for the right to compete in able-bodied competition.
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