Police said protesters threw urine bottles and smashed the glass of a police car and several shop windows. One person was arrested, another 17 were released with warnings.
Kyle Rittenhouse took a rifle and joined a group of other armed men during the Kenosha protests in late August last year, which began after police shot seven times a black suspect Jacob Blake in the back.
Then he shot Joseph Rosenbaum, who chased the young man and threw a plastic bag at him, and then Anthony Huber, who hit the young man with a skateboard. Rittenhouse also wounded Gaige Grosskreutz, who was carrying a pistol.