PRETORIA, South Africa (AP) -- A shaken Oscar Pistorius refused to look at a gruesome photo of his slain girlfriend's bloodied head on Wednesday, telling a prosecutor through tears, ''I don't have to look at a picture. I was there.''
''It's time that you look at it,'' chief prosecutor Gerrie Nel said during a fierce first day of cross-examination in which he doggedly pressed the double-amputee Olympian to ''take responsibility'' for killing Reeva Steenkamp.
The 27-year-old Pistorius is charged with premeditated murder in the Valentine's Day 2013 shooting of Steenkamp, who was hit three times - in the head, arm and hip - as she cowered behind a locked toilet door. Pistorius says he shot the 29-year-old model and law school graduate by mistake, thinking she was a dangerous intruder.
Gasps could be heard in the courtroom from spectators, including the dead woman's mother, June, when the police photo suddenly appeared on multiple TV screens showing Steenkamp's head turned to the side, her blonde hair drenched in blood and a mass of tissue on the back and upper parts of her skull, her eyes closed.
Pistorius turned away and refused to look at the image, even as the prosecutor insisted he do so and face up to what he did.
''I will not look at a picture where I'm tormented by what I saw and felt that night,'' Pistorius said, becoming distraught and breaking into sobs. ''As I picked Reeva up, my fingers touched her head. I remember. I don't have to look at a picture. I was there.''
Wednesday's heated questioning began with the showing of a video, first broadcast on Sky News, of the star athlete firing a gun at a watermelon at a shooting range. Pistorius can be heard saying the melon was ''softer than brains'' as it exploded when the bullet hit, and calling the powerful .50-caliber handgun he was using a ''zombie stopper.''
''You know the same happened to Reeva's head,'' Nel told Pistorius. ''It exploded.''
''You killed her. You shot and killed her,'' the prosecutor said. ''Take responsibility for what you've done, Mr. Pistorius.''
Defense lawyer Barry Roux objected to the showing of the gun video, saying it was inadmissible character evidence and amounted to a legal ''ambush'' by the prosecution.
Nel also attempted to poke holes in Pistorius' version of the fatal night, including his reversal of a claim in court documents a year ago that he went out onto a balcony at his home before the shooting. The runner now says he went to the edge of the balcony but did not step outside. The discrepancy could be significant because Pistorius says a noise in the bathroom alerted him to a possible intruder, which would have been harder to hear if he were outside.
Nel tried to pin Pistorius down on whether he meant to fire into the toilet door at a perceived intruder. Pistorius said he didn't intend to shoot ''anyone'' and that he fired ''before thinking'' because he thought his life was in danger.
This prompted Nel to accuse him of weighing the legal implications of the question before answering.
Pistorius said he was merely trying to be careful with his answers because the stakes are high.
''My life is on the line,'' he said, to which Nel retorted: ''Reeva doesn't have a life anymore, because of what you've done.''
Attempting to dismantle a sympathetic image of Pistorius the defense sought to create during three days of testimony, Nel pressed the athlete to explicitly acknowledge that he killed Steenkamp.
''I made a mistake,'' Pistorius said.
''What was your mistake?'' Nel shot back.
''I took Reeva's life,'' Pistorius said.
Nel also questioned the defense's portrayal of Pistorius as a good role model. The prosecution depicts him as an angry hothead with a gun obsession.
The prosecutor asked Pistorius if people looked up to him as a sporting hero, if he would hide anything and if he lived by Christian principles.
''I'm here to tell the truth, I'm here to tell the truth as much as I can remember,'' said Pistorius, who faces a possible prison term of 25 years to life if convicted of premeditated murder.
''I'm human. I have sins,'' he added.
Torchia reported from Johannesburg.