PRETORIA, South Africa: Wrapping up five days of relentless cross-examination of Oscar Pistorius at his murder trial, the chief prosecutor insisted Tuesday that he intentionally shot his girlfriend to death after they argued and — in a final exchange — urged the Olympic athlete to take responsibility for the Valentine’s Day killing.

“Who should we blame for the fact that you shot her?” prosecutor Gerrie Nel asked Pistorius. It came right at the end of Nel’s intense scrutiny of nearly every aspect of the double-amputee runner’s story that he killed Reeva Steenkamp last year after mistaking her for a dangerous intruder.

“I don’t know, my lady, I was scared,” Pistorius replied, his voice cracking slightly as he addressed the judge and maintained his argument that he shot through a toilet cubicle door in his home at a perceived intruder who he thought was about to attack him.

It’s a story the prosecutor dismissed as “improbable.”

Nel accused Pistorius, the one-time star of disabled sport, of tailoring evidence and concocting the version to cover up that he killed Steenkamp intentionally after a late night fight.

Pistorius steered away from a direct response to the prosecutor’s invitation to take the blame for Steenkamp’s killing, saying only that he opened fire because he believed his life was under threat. That remark drew barbed follow-up questions from Nel.

“We should blame somebody ... Should we blame Reeva?” asked Nel, who has harshly criticized Pistorius as someone who is unwilling to take responsibility for his actions.