A grand jury has failed to indict Darren Wilson, 28, in the August shooting of unarmed teenager Michael Brown in Ferguson, Missouri, the St. Louis County Prosecutor announced Monday. The panel completed its deliberations Monday after considering evidence presented by prosecutors on whether Wilson should face charges for killing Brown, 18, who some witnesses said was surrendering at the time he was shot six times.

The charges the grand jury could consider were first-degree murder, second-degree murder, voluntary manslaughter and involuntary manslaughter. 

St. Louis County Prosecutor Robert McCulloch said Monday evening Wilson, who is white, would not face charges for killing Brown, who was black. Many said the killing was a symptom of the police force’s history of brutality and racism toward Ferguson’s mostly black population. Residents of Ferguson have eagerly awaited the grand jury’s decision, which could have come as late as January.

"Eyewitness accounts must always be challenged against the physical evidence," McCulloch said. He detailed at length the evidence the grand jury examined. "There was a full investigation of all evidence."

"The duty of the jury is to separate fact from fiction," McCulloch. After an exhaustive review, the jurors found no evidence to return an indictment against officer Wilson, the prosecutor said.

State officials, anxious over a volatile response to the grand jury’s decision, ramped up security in the St. Louis area in the week leading up to the announcement. The FBI Friday sent 100 agents to St. Louis to help maintain order should any problems arise. Additional FBI personnel were told to be available should the agency need more people in Ferguson, according to ABC News.

Missouri Gov. Jay Nixon last week declared a state of emergency, paving the way for the National Guard to be activated. Nixon’s decision to deploy the National Guard “to provide security at command posts” angered Ferguson protest leaders, who said the Guards’ presence would only make tensions between protesters and law enforcement worse. The move was also an indication state officials believed protests in the wake of the announcement would turn violent.

Additional measures were taken before the grand jury decision, including closing several schools in the area because of “heightened anxiety and activity,” Jennings School District superintendent Tiffany Anderson told the St. Louis Post-Dispatch. “We thought it would be better for students and staff to extend the holiday at this point," she said. Anderson said the decision was not based on any recommendation from law enforcement.

U.S. President Barack Obama has urged protesters to keep calm following the announcement. “First and foremost, keep protests peaceful,” the president said in an interview with ABC’s “This Week” that was taped last week. “This is a country that allows everybody to express their views, allows them to peacefully assemble, to protest actions that they think are unjust, but using any event as an excuse for violence is contrary to rule of law and contrary to who we are.” Michael Brown’s father, Michael Brown Sr., and Attorney General Eric Holder also called on protesters to refrain from violence.

Whether Wilson would face charges for killing Brown has been debated since Wilson shot the teen Aug. 9. Previous reports suggested Wilson would not be indicted, a hunch supported by data that has shown white officers are less likely than civilians to be charged for shooting black men. 

Many of the facts presented to the grand jury in Wilson’s case are sealed tight. McCulloch initially said the evidence would be released in the absence of an indictment, but concerns over the jury’s and witnesses’ safety have led prosecutors to reconsider making some of the evidence public