South African "Blade Runner" Oscar Pistorius, a double amputee who became one of the biggest names in world athletics, was charged on Thursday with shooting dead his girlfriend at his home in Pretoria.
Police said they had opened a murder case after a 30-year-old woman was found dead at the track star's house after an incident in the upmarket Silverlakes gated complex on the outskirts of the capital.
"At this stage he is on his way to a district surgeon for medical examination," police brigadier Denise Beukes told reporters outside the heavily guarded residential complex.
Pistorius and his girlfriend, Reeva Steenkamp, had been the only people in the house at the time of the shooting, Beukes, said, and witnesses had been interviewed about the incident, which happened in the early hours of the morning.
"We are talking about neighbors and people that heard things earlier in the evening and when the shooting took place," she said. Earlier, police said a 9mm pistol had been found at the scene.
"When a person has been accused of a crime like murder they look at things like testing under the figure nails, taking a blood alcohol sample and all kinds of other test that are done. They are standard medical tests," Beukes said.
Pistorius is due to appear in a Pretoria court after 1200 GMT.
Before the murder charge was announced, Johannesburg's Talk Radio 702 said the 26-year-old 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' complex is surrounded by a three meter 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," Britain's 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.
Steenkamp's colleagues were distraught.
"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."
Pistorius, who races wearing carbon fiber 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 400 meter semi-finals in London 2012.
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 $2 million a year.
In last year's Paralympics he suffered his first loss over 200 meters 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.
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 CEO Jon Sigurdsson told Reuters. "It is completely premature to discuss or speculate on our business relationship with him."
Neighbors 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 Silverlakes resident, who did not want to be named.
"Oscar is a good guy, an upstanding neighbor, and if he is innocent I feel for this guy deeply," he said.