(USA TODAY) Olympic runner Oscar Pistorius, breaking down frequently, testified at his murder trial Tuesday about the harrowing night he shot and killed his girlfriend, Reeva Steenkamp, telling the court he thought he was firing at an intruder.
Pistorius, 27, said he was awakened in the early hours on Valentine's Day last year by what he thought was the sound of a window being opened in his bathroom, causing him to believe that someone had broken into the apartment.
"That's the moment when everything changed," he told the court in Pretoria, South Africa.
"The first thing that ran through my mind was that I needed to arm myself and protect Reeva and I," a tearful Pistorius told the court.
He said he was "overcome with fear" and started shouting for the purported robber to get out.
The double-amputee track star, known as Blade Runner for his prosthetic leg, is accused of killing his girlfriend during an argument by firing four shots through a locked bathroom door. He insists he thought he was firing at an intruder.
"I whispered for Reeva to get down and phone the police," he said.
He told the court that his ears were ringing after he fired his weapon, and that he eventually went back to the bedroom to check on the 29-year-old Steenkamp. He said he kept calling for her, looking for her under the bed and behind the curtains.
"At that point, it dawned upon me that it could be Reeva who was in the toilet," he said.
Eventually, Pistorius said, he grabbed a cricket bat, broke down the bathroom door, and saw her body on the floor.
"I unlocked the door. ... And I sat over Reeva and I cried. I don't know how long I was there," he said, sobbing openly.
He said she "wasn't breathing."
The wrenching testimony prompted a loud sob in the courtroom from Pistorius' sister, Aimee, which in turn triggered sobbing and loud wails from the athlete.
As the judge called an adjournment, Pistorius' brother, Carl, rushed to his side and held him in a tight embrace as he was led from the courtroom, Times Live.comreports.
Earlier, Pistorius was asked by the court to remove his prosthetic legs and stand by the door that he had fired into last year. The door, which has four bullet holes, was brought into the court as evidence.
The Paralympian also acknowledged that he and Steenkamp sometimes had troubles in their relationship but that they sorted them out, were in love and were planning a life together.
Pistorius said he was "besotted" with Steenkamp when they started dating and "if anything, I was maybe more into her than she was at times with me."
His defense attorney presented an extensive list of intimate cellphone messages between the couple, some sent in the days before the shooting, to try and show that they were loving and tender with each other. Prosecutors say Pistorius was often jealous and overbearing in his relationship.
Pistorius referred to a phone message Steenkamp sent him in late January 2013 when she said she was sometimes "scared" of the double-amputee Olympic athlete, who "picked" on her. The prosecution presented the message earlier in the trial as an indicator of Pistorius' threatening behavior.
Pistorius said Tuesday that the couple had a disagreement at a social function that day and he was "maybe just being sensitive, insecure or jealous." Pistorius said he apologized to Steenkamp and sent her a message saying: "I want to talk to you. I want to sort this out. … I'm sorry for the things that I say without thinking."
"My lady, I think it was a bad day in our relationship," Pistorius said, addressing the judge who will ultimately deliver a verdict in the trial that began last month.
Defense lawyer Barry Roux asked Pistorius if the unhappiness in their relationship had passed and Pistorius replied yes.
Pistorius was being led through questions by Roux, with the defense attempting to counter accusations that the runner was a reckless hothead with an obsessive love of firearms and prone to outbursts of anger.
Pistorius first took the witness stand Monday, making a tearful apology to Steenkamp's family for killing her. Steenkamp's mother, June, sat in the courtroom, staring at him without expression.
Pistorius has pleaded not guilty to charges of pre-meditated murder and three firearm-related offenses. If convicted, he faces 25 years to life in prison.
Contributing: Associated Press