Barbara Jones joined by other protesters raise their hands up in the air as they protest Monday, Nov. 24, 2014, in Ferguson, Mo., more than three months after an unarmed black 18-year-old man was shot and killed there by a white policeman in Ferguson. Ferguson and the St. Louis region are on edge in anticipation of the announcement by a grand jury whether to criminally charge Officer Darren Wilson in the killing of 18-year-old Michael Brown. (AP Photo/Charlie Riedel)

Grand jury: No indictment in Ferguson

Barricades were erected, and more than 20 Missouri state troopers were seen silently assembling with rifles, 3-foot batons, riot shields and…

Lesley McSpadden, right, the mother of 18-year-old Michael Brown, watches as Brown's father, Michael Brown Sr., holds up a family picture of himself, his son, top left in photo, and a young child during a news conference Monday, Aug. 11, 2014, in Ferguson, Mo. Michael Brown, 18, was shot and killed in a confrontation with police in the St. Louis suburb of Ferguson, Mo, on Saturday, Aug. 9, 2014. (AP Photo/Jeff Roberson)

FBI issues warning to law enforcement

The FBI sent warnings to law enforcement across the country, alerting them to any potential reaction to a Missouri grand jury verdict.