Decision expected this month
Some area schools have told parents they will dismiss students early when the decision comes and many businesses near the stretch of downtown that saw the worst rioting after Brown's killing have boarded up their windows as a protective move.
Officials have said the grand jury's decision is likely to come this month.
Video and audio published over the weekend by the St. Louis Post-Dispatch showed Wilson leaving the police station and returning to it hours after the shooting.
There are conflicting accounts of what happened, with some witnesses saying Brown had his hands up in surrender when he was shot and others describing a physical altercation between Brown and Wilson.
Many protesters expressed anger at word over the weekend that Wilson may be able to return to his job if he is not indicted, although local police said he would be fired immediately if charges are brought.
Protest organizers planned to demonstrate at the Ferguson Police Department when the grand jury's decision comes back, and later at the county courthouse in Clayton.
Ferguson Mayor James Knowles expressed confidence on Monday in the city's police department and its chief, Thomas Jackson.
"Right now, what we need is continuity in the police department and the chief has made tremendous relationships with a number of protesters and so I think that's what those protesters want," Knowles said. "The conversations we have been able to have with people have been very productive. ... We need to have a mutual understanding before we can move forward."
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