A witness heard "non-stop shouting" in the home of South African athletics star Oscar Pistorius shortly before his girlfriend was shot dead, the detective leading the murder investigation said on Wednesday.
Warrant officer Hilton Botha, a detective with 24 years on the force, also told the Pretoria magistrates court in a bail hearing that police had found two containers of testosterone and needles in Pistorius' bedroom.
The athlete's defense team disputed the finding.
Pistorius, a double amputee dubbed "Blade Runner" because of his carbon fiber racing blades, sobbed uncontrollably as Botha presented his testimony about the death of Reeva Steenkamp, 29.
The law graduate and model was in the toilet of the athlete's home when she was shot dead in the early hours of February 14 - Valentine's Day. She was hit in the head, arm and hip.
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The shooting and allegations that have emerged at the hearing have stunned South Africa and millions of people around the world who regarded Pistorius, who has no lower legs, as the epitome of triumph over adversity.
"One of our witnesses heard a fight, two people talking loudly at each other ... from two in the morning to three," Botha told the court. Pistorius' first call after the incident was to the manager of his high security complex at 3.19 am, Botha said.
In an affidavit delivered on Tuesday, Pistorius said he woke in the middle of the night and thought an intruder had climbed through his bathroom window and entered the adjoining toilet.
The 26-year-old said he grabbed a 9-mm pistol from under his bed and went into the bathroom.
Pistorius - the highest-profile athlete in the history of the Paralympics - then described how he fired into the locked toilet door in a blind panic in the mistaken belief the intruder was lurking inside.
After four hours of testimony, the hearing was adjourned until Thursday. The hearing is expected to conclude this week, after the defense and prosecution have outlined their central arguments. It may then be several months before a trial. If convicted of premeditated murder, Pistorius faces life in jail.
Botha, who arrived on the scene an hour after the shooting, challenged Pistorius' affidavit.
"I believe he knew she was in the bathroom and he shot four shots through the door," the detective said, adding the angle at which the rounds were fired suggested they were aimed at somebody on the toilet.
Pistorius had said he moved into the bathroom on his stumps - the reason he felt so vulnerable - but Botha said the shots went in a "top to bottom" trajectory, suggesting Pistorius was wearing his artificial legs when he pulled the trigger.
"It seems to me it was fired down," he said.
One of the spent rounds was recovered from the toilet bowl, Botha said.
He also cited a witness on the upscale gated community near Pretoria where Pistorius lived as saying he heard a shot, followed 17 minutes later by more shots. Another witness spoke of a shot, followed by screams, followed by more shots, he said.
After vigorous questioning from Pistorius' defense team, Botha estimated the distance between the witnesses and Pistorius' home at 300 metres.
Lead defense counsel Barry Roux also disputed Botha's reference to "testosterone", saying the substance was a legitimate herbal remedy called "test-composutim co-enzyme".
Details on the makeup of testo-composutim co-enzyme were not immediately available but administering testosterone as an anabolic agent is banned at all times under World Anti-Doping Agency rules for sports people.
The case has drawn further attention to endemic violence against women in South Africa after the gang-rape, mutilation and murder of a 17-year-old near Cape Town this month.
Members of the Women's League of the ruling African National Congress protested outside the Pretoria court on Tuesday, waving placards saying: "No Bail for Pistorius" and "Rot in jail".
The arrest of Pistorius stunned the millions who had watched in awe last year as the Olympic and Paralympic sprinter reached the semi-final of the 400 metres in the London Olympics.
But the impact has been greatest in sports-mad South Africa, where Pistorius was seen as a rare hero who had transcended the racial divides that persist 19 years after the end of apartheid.
He carried South Africa's flag at the closing ceremony of the London Olympics, and U.S. magazine Sports Illustrated named him as one of the most inspiring figures of the year.
"Many questions are being asked, but we have no answers," Sports Minister Fikile Mbalula said in a statement.
The sprinter's endorsements and sponsorships included sportswear giant Nike, British telecoms firm BT, sunglasses maker Oakley and French designer Thierry Mugler and were thought to be worth as much as $2 million a year.
In his affidavit, Pistorius said he earned 5.6 million rand ($630,500) a year and owned properties worth nearly $1 million.
However, Nike and Mugler both said they had dropped Pistorius from advertising campaigns, while cosmetics firm Clarins said it was recalling its "A Man" perfume range out of "respect and compassion towards the families involved".