Eight people were arrested following a tense protest over the fatal police shooting of a black 18-year-old in St. Louis, officials said Friday. Demonstrators burned the American flag and police used pepper spray during a second night of unrest. Two police vehicles were damaged and one cop was hit in the arm with a brick. Rallies and marches are planned over the weekend to mark the two months since a white officer in nearby Ferguson, Missouri, shot and killed unarmed black teen Michael Brown. Some officials are concerned the gatherings could flare into violence.