South African "Blade Runner" Oscar Pistorius, a double amputee who became one of the biggest names in world athletics, will appear in court tonight charged with the Valentine's Day murder of his model girlfriend.
Police say they were called to the Silver Lakes gated community in Pretoria after neighbours heard screaming and gunshots early on Thursday morning.
They found 29-year-old model Reeva Steenkamp being treated for gunshot wounds by paramedics.
The paramedics certified her dead when they were still working on her.
Police said she had been shot four times, in the head and hands, by bullets fired from a gun owned by the sprint star.
Police are playing down reports that Steenkamp was shot while trying to surprise her boyfriend for Valentine's Day. They said a 9mm pistol was found at the scene.
Police spokeswoman Denise Beukes said the pair had been the only people in the house at the time of the shooting, adding that witnesses had been interviewed about the incident.
"We are talking about neighbours and people that heard things earlier in the evening and when the shooting took place," she said.
After being arrested Pistorius, 26, was processed through the police system.
"When a person has been accused of a crime like murder they look at things like testing under the finger nails, taking a blood alcohol sample and all kinds of other tests that are done. They are standard medical tests," Ms Beukes said.
Pistorius was due to appear in a Pretoria court last night but his hearing has been delayed until 5:00pm (AEDT) today.
"He is doing well but very emotional," his lawyer Kenny Oldwage told SABC TV, but gave no further comment.
Before the murder charge was announced, Johannesburg's Talk Radio 702 said Pistorius may have mistaken Steenkamp for a burglar.
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.
We are all devastated. Her family is in shock. They did have a good relationship. Nobody actually knows what happened.
Reeva Steenkamp's agent, Sarita Tomlinson
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 the 30-year-old 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.
| ||@reevasteenkamp What do you have up your sleeve for your love tomorrow???|
Steenkamp's colleagues were distraught following her death.
"We are all devastated. Her family is in shock," Steenkamp's agent, Sarita Tomlinson, told Reuters in tears.
"They did have a good relationship. Nobody actually knows what happened."
The victim's uncle, Mike Steenkamp, says her family is devastated.
"How it pans out at the end of the day, we will all know the story, the true story," he said.
"But [we] must never forget what Reeva stood for.
"She loved people, she loved everybody, and it was her heart that went out."
Pistorius, who races wearing carbon fibre prosthetic blades after he was born without a fibula in both legs, is 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 200m 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.
Respected worldwide for triumphing over his disabilities to compete on a level playing field with able-bodied athletes, his sponsorship deals are thought to be worth $US2 million a year.
Pistorius is sponsored by British telecoms 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 spokeswoman said before Pistorius was charged.
A Nike spokesman 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".
Pistorius also has a sponsorship deal with Icelandic prosthetics manufacturer Ossur.
"I can only say that our thoughts and prayers are with Oscar and the families involved in the tragedy," Ossur chief executive officer Jon Sigurdsson said.
"It is completely premature to discuss or speculate on our business relationship with him."
South Africa's M-Net cable TV channel said it was pulling adverts featuring Pistorius off air immediately after blanket coverage of the arrest.
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 Silver Lakes 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.