Oscar Pistorius became distraught when he was shown a graphic photo of his dead girlfriend Reeva Steenkamp by the prosecution at his murder trial in South Africa.
The BBC reports the prosecutor shocked the court by showing a photo of the gunshot injury Ms Steenkamp sustained, when Pistorius shot her last year.
"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 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 Pistorius, 27, intentionally killed Ms Steenkamp, 29, on 14 February last year by firing a gun through a bathroom door at her after a row at his Pretoria home.
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.
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 Pistorius to compose himself, the BBC reports Mr Nel sought to highlight what he said were inconsistencies in the accused'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," Pistorius replied. "I am pleading not guilty because what I'm accused of didn't happen."