South African Olympian Oscar Pistorius, the double amputee "Blade Runner" who became one of the biggest names in world athletics, has been charged with murder.
Officials allege that he shot his girlfriend, Reeva Steenkamp, dead at his home.
Police said they had opened a murder case after a 30-year-old woman died at the track star's house after an incident in the Silverlakes gated complex.
"At this stage he is on his way to a district surgeon for medical examination," police brigadier Denise Beukes said outside the heavily guarded neighborhood.
Pistorius and girlfriend Reeva Steenkamp had been the only people in the house at the time of the shooting at his residence in Pretoria, Beukes said.
Police said a 9 mm 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, other tests," Beukes said.
Pistorius is due to appear in a Pretoria court today.
Before the murder charge was announced, Johannesburg's Talk Radio 702 said the 26-year-old may have mistaken Reeva 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.
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.
Steenkamp, a model and regular on the South African party circuit, was reported to have been dating Pistorius for a year; there had been no signs of strife.
In fact, some of her last Twitter postings indicated she was looking forward to celebrating Valentine's Day on Thursday with the Olympic track star.
"What do you have up your sleeve for your love tomorrow???" she posted.
However, Beukes said police were aware of previous incidents of "domestic nature" and Pistorius is believed to keep 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 last year.
He was arrested in 2009 for assault after slamming a door on a woman; family and friends said it was just an accident and the charges were later dropped.
Reeva Steenkamp's colleagues were distraught.
"We are all devastated. Her family is in shock," her agent, Sarita Tomlinson said. "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.
He reached the 400 meter semi-finals in London 2012.
Respected worldwide for triumphing over his disabilities to compete with able-bodied athletes, his sponsorship deals are thought to be worth $2 million a year.
Oscar 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 said before hearing of the murder charge that the company was "saddened by the news, but we have no further comment at this stage."
Neighbors, as well as the Olympic community and world at large, expressed shock at the arrest of an athletic ambassador and all-around "good guy."