Oscar Pistorius became distraught as he was shown a graphic photo of his dead girlfriend Reeva Steenkamp by the prosecution at his murder trial.
“It’s time that you look at it,” chief prosecutor Gerrie Nel said, presenting the photo at the start of the first day of cross-examination.
The South African athlete, who denies murdering Ms Steenkamp, insisted he had made a “mistake”.
He says he accidentally killed her after mistaking her for an intruder.
Prosecutors say Mr Pistorius intentionally killed Ms Steenkamp on 14 February last year by firing a gun through a bathroom door at her after a row at his Pretoria home.
The 27-year-old Olympic and Paralympic sprinter, who is a double amputee, faces life imprisonment if convicted of murdering the 29-year-old model, reality TV celebrity and law graduate.
Following legal arguments on Wednesday morning, Mr Nel showed video footage of the athlete at a gun range shooting a watermelon.
Mr Nel then said the watermelon had exploded in the same way as Ms Steenkamp’s head – and showed the graphic photo. He asked Mr Pistorius to look at it and take responsibility for his actions.
An emotional Mr Pistorius turned away from the image on a monitor screen and said: “I’ve taken responsibility… but I will not look at a picture where I am tormented by what I saw and felt that night… I remember. I don’t have to look at a picture, I was there.”
He added: “I made a mistake. My mistake was that I took Reeva’s life.”
After an adjournment to allow Mr Pistorius to compose himself, Mr Nel sought to highlight what he said were inconsistencies in the athlete’s statements, questioning his claims that police had tampered with items in his home after the shooting.
“I am not pleading not guilty because the scene was contaminated,” Mr Pistorius countered. “I am pleading not guilty because what I’m accused of didn’t happen.”
The BBC’s Andrew Harding, who was in court in Pretoria, says in the opening moments of cross examination, Mr Nel showed the highly combative style Mr Pistorius can now expect from him in the coming days.
Gerrie Nel: Fierce prosecutor
Gerrie Nel is known for his no-nonsense attitude inside the courtroom and is one of South Africa’s most respected legal minds.
With more than 30 years’ experience he has a string of successful prosecutions under his belt and is no stranger to high-profile cases. He prosecuted former police boss and Interpol’s ex-head Jackie Selebi on corruption charges, once calling him an “arrogant liar” during cross examination.
Those who know him praise his meticulous attention to detail and his “fearlessness”. He was junior prosecutor in the murder case of anti-apartheid activist Chris Hani in 1993.
He was also the founding head in 1999 of the Gauteng province division of South Africa’s elite police and prosecution unit the Hawks, then known as the Scorpions.
Earlier, while being questioned by his lawyer Barry Roux, Mr Pistorius told the court he had tried to revive Ms Steenkamp, who was hit by three of four pistol rounds he fired through the door.
“I checked to see if she was breathing and she wasn’t,” he said. “I could feel the blood was running down on me.”
He said he had managed to carry Ms Steenkamp downstairs, where neighbours had tried to administer first aid before paramedics arrived.
“The paramedics arrived. They asked for some space to work so I stood up,” Mr Pistorius said. “Reeva had already died whilst I was holding her, before the ambulance arrived, so I knew there was nothing they could do for her.”
Before Mr Roux ended his questioning, he asked Mr Pistorius if he had intentionally killed Ms Steenkamp.
“I did not intend to kill Reeva or anybody else for that matter,” he replied.
If Mr Pistorius is acquitted of murder, South African law stipulates that the court must consider the separate, lesser charge of culpable homicide, or manslaughter, for which he could receive between six and 15 years in prison.
Mr Pistorius also faces charges of illegally firing a gun in public and of illegally possessing ammunition, both of which he denies.
There are no juries at trials in South Africa, and his fate will ultimately be decided by the judge, assisted by two assessors.
Mr Pistorius said in his statement at the start of the trial that he woke in the early hours and walked on his stumps to the balcony, pulled in two fans, closed the sliding door and drew curtains. He said that shortly before he had spoken to Reeva, who was in bed beside him.
He said he rejected prosecution claims that a witness heard arguing coming from the house before the shooting.
2. Bathroom noise
Mr Pistorius said he heard the bathroom window sliding open and believed that an intruder, or intruders, had entered the bathroom through a window which was not fitted with burglar bars.
“Unbeknown to me, Reeva must have gone to the toilet in the bathroom at the time I brought in the fans,” he said.
Mr Pistorius said he approached the bathroom armed with his firearm, to defend himself and his girlfriend, believing Ms Steenkamp was still in bed.
Both sides agree four bullets were fired. Ms Steenkamp was hit three times.
Mr Pistorius said he fired his weapon after hearing a noise in the toilet which he thought was the intruder coming out of the toilet to attack him and Ms Steenkamp.
He said he was in a fearful state, knowing he was on his stumps and unable to run away or properly defend himself.
Mr Pistorius said he rejected claims that he was on his prostheses when he shot at the door.
A witness told the trial she woke to hear a woman screaming and a man shouting for help. She said that after the screams she heard four shots.
Mr Pistorius said he went back to the bedroom after shooting at the toilet door, still shouting for Reeva. Lifting himself up onto the bed, he felt over to the right hand side of it and noticed Ms Steenkamp was not there.
Mr Pistorius said this was when he realised she could have been in the toilet.
5. Toilet door
Mr Pistorius said he went back to the bathroom but the toilet was locked, so he returned to the bedroom, pulled on his prosthetic legs, turned on the lights before bashing in the toilet door with a cricket bat.
Forensics expert Johannes Vermeulen told the court that the height of the marks on the door caused by the cricket bat suggest Mr Pistorius was on his stumps at the time.
6. Emergency calls
Mr Pistorius’s defence team say he then called security at the gated housing complex and a private paramedic service before carrying Ms Steenkamp downstairs.
A security guard claimed it was the other way round, and he had called Mr Pistorius first after reports of gunfire. However, phone records shown to the court revealed Mr Pistorius called the estate manager at 3:19am, a minute later he called the ambulance service and at 3:21am he called estate security.
A minute later he received an incoming call – estate security calling him back.
According to police phone expert Francois Moller, Mr Pistorius called his friend Justin Divaris a short time later and just after 4:00am he called his brother Carl.