A high school graduation photo of Michael Brown rests on top of a snow-covered memorial Monday, Nov. 17, 2014, more than three months after the black teen was shot and killed nearby by a white policeman in Ferguson, Mo. The shooting sparked weeks of violent protests and Missouri Governor Jay Nixon declaring a state of emergency today as a grand jury deliberates on whether to charge Ferguson police officer Darren Wilson in the death. A woman looks at a memorial in the middle of the street Monday, Nov. 17, 2014, more than three months after black teen Michael Brown was shot and killed there by a white policeman in Ferguson, Mo. This photo shows a memorial in the middle of the street more than three months after black teen Michael Brown was shot and killed there by a white policeman Monday, Nov. 17, 2014, in Ferguson, Mo. The shooting sparked weeks of violent protests and the Missouri Governor declaring a state of emergency as a grand jury deliberates on whether to Ferguson police officer Darren Wilson in the shooting. (AP) - As a grand jury weighs possible criminal charges against the police officer who fatally shot Michael Brown, Missouri's governor has again activated the National Guard in an effort to avoid more unrest in the St. Louis suburb of Ferguson. Unlike in August, when Gov. Jay Nixon asked the troops to help provide security after protests turned occasionally violent, his latest move is pre-emptive. It comes ahead of any decision on whether Ferguson Police Officer Darren Wilson, who is white, will be indicted for the Aug. 9 shooting death of the black 18-year-old. There also are some operational differences this time. When Nixon last declared a state of emergency, he put the Missouri State Highway Patrol in charge of a unified local police command and later activated the National Guard to provide security around the command center. This time, Nixon said the St. Louis County Police Department would be in charge of security in Ferguson and would work with the Highway Patrol and St. Louis city police as part of a unified command to "protect civil rights and ensure public safety" in other jurisdictions. "My hope and expectation is that peace will prevail," Nixon said Monday. But we have a responsibility - I have a responsibility - to plan for any contingencies that might arise. But St. Louis County prosecutor Bob McCulloch has said that he expects the grand jury to reach a decision in mid-to-late November. It's looking into potential civil rights violations in Wilson's actions and the police department's overall practices, including whether officers used excessive force and engaged in discriminatory practices. On the day of the shooting, Wilson had spotted Brown and a friend walking in the middle of a street and told them to move to the side, but they did not. According to a St. Louis Post-Dispatch report based on sources the newspaper did not identify, Wilson has told authorities he then realized Brown matched the description of a suspect in a theft minutes earlier at a convenience store. Brown's shooting stirred long-simmering racial tensions in Ferguson, where two-thirds of the residents are black but the police force is almost entirely white. Associated Press writer Summer Ballentine contributed to this report.