Wisconsin police fatally shot an apparently unarmed African-American teenager.
Koval said that a struggle between the suspect and the officer arose and the teen was fatally shot, according to broadcaster WKOW.
Madison Police have not identified the victim, but his mother, identified him as Anthony Robinson.
Koval said it's not clear if Robinson had any sort of weapon.
The shooting prompted dozens of people to protest at the site of the killing. The shooting comes at a time of increased scrutiny of police violence against minorities across the US.
Videos published on social media showed around 100 protesters at the scene of the shooting chanting slogans like, "Who can you trust? Not the police," in front of a row of officers.
Protests have been held in Los Angeles and Washington in recent days over police killings of unarmed, minority men.