Prosecutor Gerrie Nel went on the attack by showing graphic images of Reeva Steenkamp's head wound and telling Pistorius: "You should take responsibility."
Pistorius again broke down in tears as prosecutor Nel focused on the runner's love of weapons during cross-examination of the runner as his murder trial continues.
Nel flashed up a graphic image of Steenkamp's head taken shortly after Pistorius blasted her to death in his bathroom on Valentine's Day last year.
The gruesome image showed her dead with blood and gore pouring from a deep bullet wound.
Pistorius refused to look at it, but Nel insisted he did so, saying: "take responsibility Mr Pistorius for what you've done!"
In a frantic tone and fighting back sobs, the Olympian and Paralympian answered: "I've taken responsibility but I will not look at the picture. I remember it. I don't need to look at a picture: I was there!"
He then collapsed in tears. The session then adjourned to give him time to compose himself.
Earlier in the exchange, judge Thokozile Masipa told Nel his line of questioning was "unfair" by comparing video of Pistorius at a shooting range with what he did to her.
In the footage, Pistorius is seen shooting a watermelon with a pistol and then comparing the effect of the bullet on the fruit to a brain.
A voice thought to be Pistorius remarks: "It's not as soft as brains but f*** it is a zombie stopper."
Pistorius told North Gauteng High Court: "I've seen this video before. I didn't remember the words zombie stopper [...] It makes me v upset to hear those words, but I cannot see the relevance of comparing a human with a watermwelon. I didn't at any point compare it to a human."
Nel claimed he did make the comparison by mentioning the word "brains."
Pistorius denies murder and claims he mistook Steenkamp for an intruder. The prosecution alleges he killed her following an argument between the couple.
The trial continues.