More troops deployed in Ferguson

National Guard soldiers stand in formation outside the Ferguson Police Department following a night of rioting in Ferguson, Missouri November 25, 2014. [Photo/Agencies]

The grand jury decision shifted the legal spotlight to an ongoing US Justice Department investigation into whether Wilson violated Brown's civil rights by intentionally using excessive force and whether Ferguson police systematically violate rights by using excessive force or discrimination.

Holder said he had been briefed by Justice Department officials overseeing federal probes surrounding Brown's death, but did not say when investigators might complete their work.

Obama asked Americans on Tuesday to be "constructive" by engaging in debate about racial tensions and law enforcement. He also said demonstrators who engage in criminal acts should be prosecuted.

Brown family lawyer Benjamin Crump said the grand jury proceedings were unfair because the prosecutor in the case had a conflict of interest and Wilson was not properly cross-examined.

"The process should be indicted," Crump said, adding that the family wants police to be equipped with body video cameras to provide an indisputable account of their actions.

Schools in Ferguson and its surrounding cities were closed on Tuesday and city offices in Ferguson were also shut.

"This is going to happen again," said Ferguson area resident James Hall, 56, as he walked past a smoldering building. "If they had charged him with something, this would not have happened to Ferguson."

In the city of St. Louis, where windows were broken and traffic was briefly stopped on a major highway overnight, Police Chief Sam Dotson vowed a stronger response on Tuesday night.

About 1,000 demonstrators gathered outside a federal courthouse in St. Louis blocking a road and chanting, "This what democracy looks like."

Protests were also held on Tuesday in New York, Atlanta, Baltimore, Chicago, Philadelphia and Washington.

Wilson, who could have faced charges ranging from involuntary manslaughter to first-degree murder, thanked his supporters in a letter attributed to him on a Facebook page for those who have rallied to his side, saying "your dedication is amazing."

Attorneys for Wilson, who was placed on administrative leave since the shooting, said he had been following his training and the law when he shot Brown.

Wilson told the grand jury Brown had tried to grab his gun and he felt his life was in danger when he fired, according to documents released by prosecutors.

"I said, 'Get back or I'm going to shoot you,'" Wilson said, according to the documents. "He immediately grabs my gun and says, 'You are too much of a pussy to shoot me.'"