Story highlights Pistorius' sentence increased to 13 years and five months for Reeva Steenkamp's murder

The decision is "justice for Reeva," a family spokeswoman says

(CNN) Reeva Steenkamp "can now rest in peace," her family said Friday, after a South African high court more than doubled Oscar Pistorius' sentence for her killing.

The Supreme Court of Appeal increased his sentence to 13 years and five months for the murder of his girlfriend, Steenkamp. It issued the ruling after the prosecution appealed his previous sentence of six years as too lenient.

The former Olympic and Paralympic sprinter killed Steenkamp at his home in an upscale Pretoria neighborhood on Valentine's Day 2013 -- an act he says was an accident after he mistook her for an intruder. The prosecution called it a deliberate act after the two had an argument.

The court's decision is "justice for Reeva," her family's spokeswoman said, adding that they hope "this is the end of the road and that everyone can move forward."

Prosecutor Gerrie Nel argued that Pistorius' sentence was "shockingly lenient," while the defense sought to dismiss the appeal.

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