For a second day, some protests over a grand jury's decision not to indict the police officer who fatally shot 18-year-old Michael Brown in Ferguson, Missouri, have focused on disrupting commerce.

Here's a look at Saturday's developments and some background on the case:

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PROTESTS AND ARRESTS

Demonstrators marched through a Trader Joe's grocery store in Brentwood, about 10 miles south of Ferguson, around noon Saturday. After leaving, they briefly blocked a road near Interstate 170.

The action came a day after crowds of protesters prompted authorities to temporarily close three large shopping malls in suburban St. Louis. A demonstration later Friday night in front of Ferguson's police and fire departments led to 16 arrests.

Other protests across the country focused on Black Friday, with about 200 people demonstrating along Chicago's popular Magnificent Mile shopping district and 11 people arrested at a mall in Raleigh, North Carolina.

Numerous storefronts in the Ferguson area still have their windows covered with plywood after the looting and violence in the immediate aftermath of the grand jury announcement Monday. But many merchants added spray-painted messages indicating that they were open ahead of Small Business Saturday.

In a separate Missouri demonstration, protesters are set to march from Ferguson to Gov. Jay Nixon's mansion in Jefferson City. The 120-mile march will take seven days and was organized by the NAACP.

Organizers say the purpose is to call for new leadership in the Ferguson police department and for police reforms in the St. Louis suburb and throughout the U.S.

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FAMILIES OF BROWN, MARTIN MEET

Brown's father, Michael Brown Sr., attended a prayer vigil Friday night in Miami Gardens, Florida. He met with Sybrina Fulton and Tracy Martin, whose 17-year-old son Trayvon Martin was killed in 2012 by a neighborhood watch volunteer.

Tracy Martin told Miami television station WFOR he offered Michael Brown Sr. encouragement and told him "God has his hands on the situation, and he's gonna be OK."

The vigil was part of the annual Gospel Explosion Concert hosted by rapper Flo Rida.

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THE CASE

Brown, who was black, was unarmed when he was fatally shot by Ferguson police Officer Darren Wilson, who is white, after an altercation Aug. 9 in a local street. The shooting stirred racial tensions and prompted several days of strong and at times violent protests in Ferguson, a predominantly black community patrolled by a mostly white police force.

A grand jury later was assembled, and its nine white and three black members spent three months hearing more than 70 hours of testimony from 60 witnesses. Their decision not to indict Wilson was announced Monday night.

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WHAT'S NEXT

The U.S. Justice Department has its own investigation into possible civil rights violations that could result in federal charges for Wilson, but investigators would need to satisfy a rigorous standard of proof. The federal agency also has launched a broad investigation into the Ferguson Police Department.