Ferguson: After a Missouri grand jury did not charge a white police officer in relation to the shooting that resulted in the death of black teen Michael Brown, his family and supporters are pinning their hopes on federal investigations.

The Justice Department launched its own probes in the wake of the August 9 shooting of 18-year-old Brown, who was unarmed, by officer Darren Wilson in the St Louis suburb of Ferguson.

One arm of the probe is to determine whether Wilson violated Brown’s civil rights.

The second to look at whether the Ferguson police department engages in racial profiling or employs excessive force. The case has garnered much attention and the verdict resulted in violent protests in the state.

After protesters looted Ferguson businesses and set fire to buildings on Monday, Attorney General Eric Holder tried to reassure residents who were disappointed in the legal system.

“The department’s investigations will continue to be thorough,” Holder said. “They will continue to be independent and they remain ongoing.”

He said that he hoped the probes could “restore trust” between law enforcement and members of the community.

In August, after Brown was shot dead and Ferguson was convulsed by violence, Holder quickly visited the town and said he understood how black residents were wary of the mainly white police force. “I understand that mistrust. I am the attorney general of the US. But I am also a black man,” he said.

After the grand jury’s decision was made public, President Barack Obama said that the situation in Ferguson “speaks to the broader challenges that we still face as a nation.”

“A deep distrust exists between law enforcement and communities of colour,” said Obama.

Nevertheless, more than three months after Brown’s death, the Obama administration has announced no charges, and leaks to the US media suggest federal cases may not be forthcoming.

St Louis County Prosecutor Robert McCulloch said federal and local authorities had shared all their information in their parallel investigations and that the evidence had not been sufficient to indict Wilson.

Holder, who has been seen as a champion of civil rights during his tenure as the nation’s first black attorney general, is due to leave office soon.

After the Brown family said it was “profoundly disappointed” in the grand jury’s decision, rights campaigners called on federal authorities to act.

“We may have lost one round, but the fight is not over,” civil rights firebrand Al Sharpton told reporters on Tuesday, calling for a nationwide day of protest on Saturday.