04/09/2014 at 04:35 PM EDT
A shaken Oscar Pistorius
refused to look at a gruesome photo of his 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 retorted during a fierce first day of cross-examination in which he doggedly pressed the double-amputee Olympian to "take responsibility" for killing Reeva Steenkamp.
"You shot and killed her. Say it – 'I shot and killed Reeva Steenkamp
,'" Nel told 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.
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."