FERGUSON, Mo. — A white police officer will not face charges for fatally shooting an unarmed black teenager in a case that set off violent protests and racial unrest throughout the nation.

A St. Louis County grand jury declined to indict officer Darren Wilson, 28, for firing six shots in an August confrontation that killed 18-year-old Michael Brown, St. Louis County prosecutor Robert McCulloch said Monday night.

Crowds of protesters filled streets near the Ferguson police station following the announcement. A police car and stores were set on fire, other stores were looted, gunfire was heard and bricks were hurled. Police said they had been fired on and responded with smoke bombs and pepper spray before using tear gas.

Police later said they came under heavy automatic weapon fire, and some buildings were left to burn because of the danger. County police said an officer suffered a gunshot wound, but it was unclear if it was because of the protest violence.

Protests sprang up in cities from New York to Los Angeles and remained mostly peaceful. At least half a dozen commercial airline flights into St. Louis were diverted out of concerns about the unrest.

The Federal Aviation Administration at 11:15 p.m. ET said it had restricted flights into and out of Lambert International Airport in St. Louis to “provide a safe environment for law enforcement activities.” The restriction lifts at 5:15 a.m. ET.

The grand jury’s decision had been long awaited and followed earlier Ferguson rioting that resembled war-zone news footage in this predominantly black suburb of St. Louis.