Prosecutors are continuing to spar with South African runner Oscar Pistorius over the details of the night he fatally shot his girlfriend, Reeva Steenkamp.
Pistorius returned to the witness stand Monday for his fourth day of cross-examination.
He testified that he shot after hearing a sound like the bathroom door being opened, but without seeing the door move.
Prosecutor Gerrie Nel challenged the athlete's stance that he fired in self-defense at a perceived intruder, saying he did not actually know why he fired.
"No, I'm not saying I don't know why, I've given a reason to why I fired, my lady. I thought someone was coming out to attack me."
"But you didn't fire at that person."
"I fired in the direction where I thought the attack was coming from, my lady."
"You see, Mr. Pistorius, you now have to give a lot of answers, and you know why Mr. Pistorius, it's because you know exactly, you fired at Reeva. These other versions of yours cannot work.
"It's not true my lady.
"You fired at her, you did.
Pistorius broke down after his answer, the second time the court was forced to take a break Monday. He later said the sound must have been a magazine rack moving inside the bathroom.
The prosecution also asked Pistorius about details of the shooting scene, including the blood spatter and the placement of Steencamp's personal items in his bedroom.
Prosecutors says Pistorius intentionally shot Steenkamp. Nel has used tough questioning to try to portray Pistorius as prone to anger and careless with guns, and pressed Pistorius to take responsibility for the killing.
The athlete insists he thought he was shooting at a nighttime intruder.
Pistorius is known as the "blade runner" for his carbon-fiber prosthetic legs. He has won many Paralympic Games medals, and was the first double amputee to compete in the Olympics.