The chief prosecutor pulls no punches, forcing Oscar Pistorius to take responsibility for killing Reeva Steenkamp and to look at photos of her bloodied head, as the feisty cross-examination begins.

Warning: the above video contains some distressing images towards the end, from 3.45 minutes

He is known in South Africa as “the bulldog”, and Chief Prosecutor Gerrie Nel lived up to his name in the Pretoria courtroom on Wednesday, as he began his questioning of Oscar Pistorius.

To start with, he dismissed Pistorius’s statement that he made a “mistake”, and forced the accused to say out loud that he had killed Reeva Steenkamp, asking: “You shot and killed her. Won’t you take responsibility for that?”

Later, when asking for clarification on questions, Pistorius said: “my life is on the line,” to which Mr Nel retorted: “Reeva doesn’t have a life anymore, because of what you’ve done.”

The chief prosecutor was also given permission by the judge to show a video of Pistorius at a shooting range, first broadcast in February this year, in which he is seen firing shots at a watermelon. The accused is then heard saying: “It’s not as soft as brains but f*** it is a zombie stopper.”

The effect the ammunition had on a watermelon. It exploded… You know that the same thing happened to Reeva’s head Gerrie Nel

In court, the lawyer then compared the effect of the shooting a watermelon, to shooting Steenkamp in the head, and showed photos of Steenkamp’s bloodied head on the screens in court, calling on Pistorius to look at the photos. “The effect the ammunition had on a watermelon. It exploded. Am I right?,” he said. “You know that the same thing happened to Reeva’s head. Have a look.”

The Steenkamp family’s heads were lowered, and Pistorius broke down in tears. But Mr Nel continued to urge him to look, and said: “Take responsibility for what you’ve done”. Through tears, Pistorius replied: “I am tormented by that… my fingers touched her head. I don’t have to see a picture. I remember it.”

The trial was then briefly adjourned after his lawyer objected that showing the photos was unnecessary.

June Steenkamp, Reeva’s mother, had been warned her that that the graphic photo would be shown, prosecution lawyers told reporters, adding that she was happy for Pistorius to be confronted with the image.

VIDEO BELOW: Oscar Pistorius: “I made a mistake.” Chief Prosecutor: “You shot and killed her. Won’t you take responsibility for that?” The cross-examination begins.

South Africa’s most famous athlete, known as the “blade runner” stands accused of murdering Reeva Steenkamp by shooting her four times through the toilet door of his home in the early hours of 14 February 2013.

He denies murder, but admits shooting her, believing she was an intruder. The trial is the first in South Africa to be televised, and although Pistorius has opted not to be seen on camera, the audio of his testimony is being beamed around the world.

He began giving evidence on Monday, and started his testimony with an emotional apology to Steenkamp’s family. Court was adjourned early on Tuesday after Pistorius howled in torment while giving his version of what happened on the night he killed his then-girlfriend, finishing with him beating down the toilet door to reach her body.

VIDEO: An emotional Oscar Pistorius finishes his account of the moments after he killed Steenkamp: “I felt helpless. I wanted to take her to the hospital. I had my fingers in her mouth, trying to help her breathe.”

‘Before thinking, in fear, I fired four shots’

Apart from the dramatic start to the cross-examination, and the biting exchanges between Mr Nel and Pistorius, the prosecution started chipping away at the defence case.

The accused was forced to admit that part of his bail hearing was “incorrect”, after Mr Nel asked him to clarify some differences between his testimony in court and the hearing last year, when he said he went out onto the balcony to get a fan.

Reeva doesn’t have a life anymore, because of what you’ve done Gerrie Nel

In what will become a crucial part of the trial, Pistorius was also grilled on his comment that the shooting was an “accident”: he tried to insiste that he accidently discharged his firearm, and that he didn’t intend to shoot anyone, let alone his girlfriend.

“I pulled the trigger, at that moment when I heard the noise, I didn’t have time to think,” he said, adding: “Before thinking, in fear, I fired four shots”.

Regardless of whether he intended to shoot Steenkamp, the question of whether he intended to shoot an intruder is a crucial part of the case – and could see him liable for manslaughter under South African law. There are no juries in South Africa, and the verdict of the trial will be decided by one judge and her two assessors.