A statement from the South African athlete was read out in court on Tuesday, giving his version of events for the first time. Pistorius broke down and wept uncontrollably as his lawyer read out the account.
The athlete said that he and Reeva Steenkamp, a 29-year-old model, were "deeply in love" and "could not have been happier".
On the night in question, Pistorius said that he had a 9mm handgun under the bed – a precaution that he normally took. Waking in the summer heat in the early hours of the morning, he went out to the balcony to get a fan.
The athlete had not attached his prosthetic limbs and was walking on his stumps. Suddenly he "heard a noise in the bathroom". Pistorius knew the bathroom window was open and that ladders were accessible nearby. He thought that intruders had entered the house.
"I screamed words to the effect of for him/her to get out of my house and for Reeva to phone the police," said Pistorius in his statement. "I thought Reeva was in the bed. I felt extremely vulnerable but I knew I had to protect Reeva and myself."