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.

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.

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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