Oscar Pistorius took the witness stand in South Africa on Monday and was remorseful for the death of girlfriend Reeva Steenkamp.
Pistorius, a double-amputee runner who appeared in the 2012 Olympics, is on trial for the alleged murder of Steenkamp.
Before maintaining that Steenkamp's death was accidental, Pistorius tearfully apologized to her family on Monday.
"There hasn't been a moment since this tragedy happened that I haven't thought about your family," he said as he addressed the courtroom, which included Steenkamp's mother, June.
"I wake up every morning and you're the first people I think of, the first people I pray for ... I was simply trying to protect Reeva. I can promise that when she went to bed that night she felt loved."
Pistorius claims he shot Steenkamp in the head, arm and hip through a toilet door in his home because he had mistaken her for an intruder.
Prosecutors say Pistorius intentionally killed her after a fight on Valentine's Day, 2013, and have claimed the 27-year-old is a hothead obsessed with firearms.
On Monday, Pistorius said he has suffered panic attacks since the incident and added that he has nightmares that have caused him to wake up to the "smell of blood." He also said he has been on antidepressants since Steenkamp's death. Pistorius faces 25 years to life in prison if convicted of premeditated murder.