The double-amputee runner, who has lived in virtual seclusion while on bail, said he was consumed by sorrow for fatally shooting his girlfriend, Reeva Steenkamp, in his home a year ago on Friday.
The rare statement from Pistorius was posted on his website, which carries photographs of the track star in his prime. One image shows him smiling broadly, surrounded by children giving a thumbs-up sign. Another shows him lifting the South African flag in triumph after a sprint.
"No words can adequately capture my feelings about the devastating accident that has caused such heartache for everyone who truly loved — and continues to love Reeva," said Pistorius, who told a court last year that he shot Steenkamp because he mistook her for a nighttime intruder. Prosecutors allege the track star intentionally killed her after an argument.
"The pain and sadness — especially for Reeva's parents, family and friends consumes me with sorrow," Pistorius said. "The loss of Reeva and the complete trauma of that day, I will carry with me for the rest of my life."
Pistorius also tweeted a link to his website alongside the phrase: "A few words from my heart."
His last tweet was about his foundation work on Feb. 11, 2013, three days before he killed Steenkamp in his bathroom in the pre-dawn hours. The murder trial starts March 3 in Pretoria, the capital.
The statement Friday from Pistorius, 27, was unusual because his uncle, Arnold, has normally been quoted in statements from his camp, which has sought to shield the runner from intense media and public interest in a case that transfixed many people around the world.
Steenkamp's mother, June, plans to attend the trial. No members of Steenkamp's immediate family have attended any of Pistorius' previous court dates. Pistorius also faces other firearms-related charges.
A pub owned by Steenkamp's father, Barry, in the South African city of Port Elizabeth was closed on Friday.
Beth Butler, owner of another bar in Port Elizabeth, said Valentine's Day was a particularly sad occasion for any parent to lose a child.
On Wednesday, the spokeswoman for Pistorius said he reached a settlement with a woman over an alleged assault case from 2009 because his lawyers advised him he could not fight civil and criminal legal battles at the same time. He was arrested and accused of causing an injury to Cassidy Taylor-Memmory, a guest at a party at his house five years ago, after allegedly slamming a door and then punching it.
Pistorius was the first double-amputee to run at the world championships and the Olympics. He faces a possible life sentence with a minimum of 25 years in prison before the chance of parole if he is convicted of premeditated murder in Steenkamp's killing.
A judge will deliver a verdict. There is no trial by jury in South Africa.
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