GENEVA, Ill. (AP) — The Illinois state’s attorney who was special prosecutor in the case of a white Chicago police officer convicted of killing black teenager Laquan McDonald says he won’t seek re-election.

Kane County State’s Attorney Joseph McMahon announced his decision not to run for a third term in a Tuesday letter. He didn’t give a reason. McMahon has held the post since 2010.

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McMahon was tapped in 2016 to prosecute former Chicago police officer Jason Van Dyke when Cook County State’s Attorney Anita Alvarez recused herself from the case. Van Dyke is serving a prison sentence after he was convicted of second-degree murder and aggravated battery.

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McMahon called the McDonald case “a test of our justice system” in his Tuesday letter and said he was proud to have handled it.

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