South Africa’s Supreme Court of Appeal Thursday found Oscar Pistorius guilty of killing his girlfriend Reeva Steenkamp, overturning an October 2014 ruling that convicted the former paralympian of culpable homicide. Pistorius is likely to face 15 years in jail.

A panel of five judges, headed by Justice Lorimer Eric Leach, delivered the ruling and instructed the North Guateng High Court to implement the sentence, without specifying the time. The ruling, for which Pistorius was not present, was based on the concept of “dolus eventualis” in South African law, where a person can be convicted of murder if it's proved they foresaw his or her actions might lead to death. The judge also said that the previous verdict had a "fundamental error," NBC News reported.

Pistorius stood trial after Steenkamp's death in the early hours of Feb. 14, 2013 at his Pretoria home. The 29-year-old, also known as the “bladerunner” for running on prosthetic legs, had maintained that he mistook Steenkamp for an intruder and fired at her in self defense. However, prosecutors argued that Pistorius shot Steenkamp during an argument.

"All the shots fired through the door would almost inevitably have struck the person behind it. There would be effectively no place to hide," Leach said, according to CNN.

According to Leach, Pistorius' testimony was "unacceptable," "vacillating" and "contradictory" and added that if the double-amputee Olympian feared for his life, he should have acted more rationally. Furthermore, Pistorius did not fire a warning shot and shot four times, Leach reportedly said.

The judge said the events in the case involved a “human tragedy of Shakespearean proportions."

"A young man overcomes huge physical disabilities to reach Olympian heights as an athlete. In doing so he becomes an international celebrity, he meets a young woman of great natural beauty and a successful model, romance blossoms, and then, ironically on Valentine's Day, all is destroyed when he takes her life," the judge said, according to NBC News.

Pistorius’ family said they took a note of the verdict. "The legal team will study the finding and we will be guided by them in terms of options going forward," the family said, in statement, according to the Associated Press.

A date for the former athlete’s sentencing will be announced in the capital Pretoria, where Pistorius was tried and jailed. In South Africa, punishment for a murder carries a 15-year maximum jail term. However, the punishment can be reduced under the law in exceptional circumstances.

Pistorius, who was sentenced to five years in prison following the previous ruling, was placed under house arrest in October after spending a year in jail. The trial court can also mull over whether he should be shown leniency because of his disability and because it was a first-time offense.