Police cars have been vandalized and several gunshots have been heard on the streets of Ferguson after the announcement that a white police officer will not be indicted in the shooting death of an unarmed black 18-year-old.

About 15 minutes after St. Louis County Prosecutor Bob McCulloch announced Officer Darren Wilson wouldn't be indicted, county police used a bullhorn to tell crowds outside the Ferguson Police Department to disperse, saying it had become an unlawful assembly.

Protesters hugged a barricade and taunted police, sometimes with expletives. Some chanted "murderer." Gunshots were heard down the street and somebody threw a water bottle that bounced off a police shield.

Some in the crowd reportedly tried to stop others from taking part in vandalism and other violent reactions.