Missouri's governor has again activated the National Guard in an effort to avoid more unrest in the St. Louis suburb of Ferguson.

The announcement comes as a grand jury weighs criminal charges against Darren Wilson, the white police officer who fatally shot Michael Brown. Gov. Jay Nixon gave no indication that an announcement is imminent. The prosecutor expects a decision this month.

In August, Nixon asked the troops to help quell the sometimes-violent protests that occurred nightly following the black 18-year-old's death.

There also are some operational differences this time. The St. Louis County Police Department will be in charge of security in Ferguson, working with the Highway Patrol and St. Louis city police as part of a unified command.