One person was shot at a protest in Milwaukee during a second night of unrest over the police shooting of a black man.
Officers used an armoured vehicle to retrieve the injured victim and take them to hospital, but there was no repeat of widespread destruction of property.
Some two dozen officers in riot gear confronted a group who were throwing rocks and other objects at police near where the black man was fatally shot a day earlier.
They said an injured officer was taken to hospital after a rock broke the windscreen of a squad car.
Police moved in to try to disperse the crowd and made multiple arrests after skirmishes between protesters and officers on Sunday night.
Police chief Edward Flynn said at a press conference on Sunday that the man whose death sparked Saturday night's rioting was shot after he turned towards an officer with a gun in his hand.
Flynn said the shooting was still under investigation and authorities were awaiting the results of a post-mortem examination, but that, based on the silent video from the unidentified officer's body camera, he "certainly appeared to be within lawful bounds".
At the same news conference, Mayor Tom Barrett said a still image pulled from the footage clearly showed a gun in 23-year-old Sylville K Smith's hand as he fled a traffic stop on Saturday.
Flynn declined to identify the officer who shot Smith but said he is black. The police chief said he was not sure what prompted the stop but described Smith's car as "behaving suspiciously".
After watching the officer's body camera footage, Flynn said the entire episode took about 25 seconds, from the start of the traffic stop until shots were fired.