Milwaukee, Wisconsin Mayor Tom Barrett says the National Guard is being activated in the midwestern city and will be deployed if trouble breaks out after another fatal police shooting of an African-American man.
Overnight violence in Milwaukee left six stores burned, police cars destroyed and a teenage girl wounded by gunfire. Several officers were also hurt, including one who suffered a concussion after being hit in the head by concrete.
Seventeen people were arrested.
Barrett praised Milwaukee police for what he calls their "tremendous restraint," telling reporters that not a single police shot was fired during Saturday night's trouble.
He appealed to parents not to let their sons and daughters get caught up in violence and troublemaking, saying he will impose a curfew if necessary.
Milwaukee police chief Edward Flynn identifies Saturday night's shooting victim as 23 year-old Sylville Smith and says he had a "lengthy arrest record."
Smith was shot in the chest and arm. The officer who shot him is also black.
Flynn and Mayor Barrett say an image taken from the unidentified officer's body camera shows Smith had a gun in his hand and was a credible threat to the officer. Flynn says it appears to be a lawful shooting.
Police earlier said Smith fled from police after a traffic stop when his car was "behaving suspiciously." A second suspect was arrested.
Some witnesses say Smith was unarmed. Barrett said he would like to see video released as soon as possible and says the investigation must be transparent and carried out quickly.
Saturday's shooting took place in Milwaukee's Sherman Park neighborhood, an impoverished section with a reputation for crime.
Sherman Park residents say the city has been unresponsive to their needs. Alderman Khalif Rainey, who represents Sherman Park, says Milwaukee's black residents are "tired of living under this oppression."
Rainey says he does not condone violence "but nobody can deny that there are racial problems here in Milwaukee, Wisconsin, that have to be rectified.''
The Milwaukee shooting is the latest in a series of incidents in which black men died as a result of police action, including deaths in Baltimore, New York, Baton Rouge, Chicago, and Furgeson, Missouri.
The shootings have usually been followed by protest marches and sometimes violence.
The protesters say the killings prove what they believe to be racism at the hands of police and white government officials, even though some of the officers involved in the killings have also been black.
In July, eight police officers were killed in separate shootings in Dallas and Baton Rouge, Louisiana, by gunmen who indicated they were angry about police violence against African Americans.