The double-amputee athlete is accused of shooting his model girlfriend, 30-year-old Reeva Steencamp, in the predawn hours at his home in a gated community in Pretoria, South Africa. A pistol was found at the house. According to investigators, the victim was shot four times.
Police said Pistorius was at his home after the death of Steenkamp and "there is no other suspect involved."
Police said there had been previous incidents and "allegations of a domestic nature" at Pistorius' home. Investigators were questioning neighbors and looking into reports that some of them may have heard shouts coming from the home.
Pistorius was undergoing blood alcohol and forensic tests and had made a request to be brought to court immediately, according to authorities. The 26-year-old athlete was originally scheduled to appear in court Thursday afternoon but the hearing was postponed until Friday.
Police said that earlier reports that Steenkamp may have been mistaken for a burglar did not come from the police. Several South African media outlets had initially reported that the shooting may have been accidental.
Pistorius is known as the "Blade Runner," the Olympic athlete who runs with prosthetic blades for legs. He made history in the Olympics last year in London, becoming the first double-amputee to compete in a track event.
On Wednesday, Steenkamp expressed her excitement for Valentine's Day.
"What do you have up your sleeve for your love tomorrow??? #getexcited #ValentinesDay," she tweeted.
The Associated Press contributed to this report.