Missouri's governor says the National Guard will help "in restoring peace and order" to the town of Ferguson, where there have been protests, some violent, since an unarmed black teen was shot and killed by a white police officer.

Gov. Jay Nixon's order to send in the Guard came after Sunday night's violence in which police used tear gas to clear protesters off the streets well ahead of a curfew.

Police say they were responding to vandalism, looting, gunfire and some people tossing Molotov cocktails.

Meanwhile, Attorney General Eric Holder has ordered a federal medical examiner to perform a third autopsy on Michael Brown.

The 18-year-old was shot and killed by a Ferguson, Missouri, police officer earlier this month.

The New York Times reports a preliminary private autopsy found Brown was shot at least six times, including twice in the head.

Results of a state-performed autopsy have not been released.

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