The officer was shooting at a pit bull dog that had been turned loose on police who were trying to serve what they called a "high risk" search warrant on a house suspected of narcotics activity. A police spokeswoman says the bullet hit concrete and ricocheted into the arm of the boy who wasn't in the line of fire.
The boy's injury is not life-threatening and he was treated at a local hospital.
The incident happened at 7:30 p.m., but tensions grew later as TV news crews arrived to cover the event. About 75 to 100 people gathered in the north Minneapolis neighborhood and shouted at police and journalists.
The windows were broken out of one news van and a city bus, and a vehicle was set on fire. Two reporters for the Star Tribune of Minneapolis were assaulted and suffered minor injuries, according to an editor at the newspaper. A photographer for the St. Paul Pioneer Press was also injured: hit in the back of the head by some kind of thrown object. According to an editor at that newspaper, the photographer was taken to the hospital to get the wound sewn up.
Officers late Thursday still had not been able to search the house that originally brought them to the neighborhood.
Thursday's violence was the latest in a series of unrelated but tension-producing incidents in the Twin Cities.
Last week, dozens of people gathered in another north Minneapolis neighborhood to protest when two police officers shot a 19-year-old man who threatened them with a handgun.
Three weeks ago, a Minneapolis police officer was killed in a shootout with a woman who lived in a public housing complex. Her niece had called police to the scene after the woman allegedly scared neighbors by waving a gun.