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The Illinois attorney general is challenging the sentence of a former Chicago police officer found guilty of fatally shooting a black teenager more than a dozen times as he walked away.

Jason Van Dyke was sentenced in January to six years and nine months in prison after he was found guilty of second-degree murder and 16 counts of aggravated battery in the killing of Laquan McDonald in October 2014.

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Prosecutors had initially asked for Van Dyke, 40, to be sentenced to a minimum of 18 years, although the state's sentencing guidelines allowed a term of 96 years or more — six years for each shot the former officer fired.

Illinois Attorney General Kwame Raoul and Kane County State's Attorney Joseph McMahon, the special counsel in Van Dyke's trial, said Monday that they filed a petition with the state Supreme Court to review whether the law was followed when the sentence was handed down.

“It is important that a police officer was held accountable for criminal conduct,” McMahon said in a press release. “But we argued at the sentencing hearing that Jason Van Dyke should be sentenced for the aggravated battery with a firearm convictions."

Instead of Van Dyke's sentence being based on his conviction for the 16 counts of aggravated battery, it was for the second-degree murder conviction, which meant less time in prison.

McDonald was shot 16 times, some striking him in the back as he was moving away from Van Dyke and other officers responding to reports the teenager was carrying a knife and breaking into cars in the city's Southwest Side. McDonald, 17, was holding a folded knife when he was shot.

Van Dyke said at his trial that he shot McDonald because he feared for his life, but dashcam footage showed that the former officer was moving toward McDonald as the teenager walked away.