A member of the National Guard cordons off a staging area inside a shopping center parking lot in Ferguson, Missouri August 21, 2014. [Photo/Agencies]

FERGUSON, Mo.- The governor of Missouri ordered the withdrawal on Thursday of National Guard troops from riot-torn Ferguson, where tensions have eased after sometimes violent protests were staged nightly since police killed an unarmed black teenager.

Peaceful demonstrations overnight were the calmest street gatherings in the small St. Louis suburb since riots erupted over the Aug 9 shooting of 18-year-old Michael Brown by a white police officer.

Police images fuel outrage in Missouri and beyond

The controversial shooting by Officer Darren Wilson prompted angry demonstrations along with looting and random gunfire from largely black crowds. Police have used tear gas and heavy armored vehicles to clear the streets and the Missouri National Guard was called in to help.

But the crowds have thinned, and the mood is decidedly less tense. Police said six people were arrested overnight - far fewer than the scores detained on earlier nights of racial unrest.

Governor Jay Nixon ordered the National Guard to begin withdrawing from Ferguson, saying in a statement: "We continue to see improvement."

"Things are de-escalating," said Roy Harris outside Original Reds B-B-Q, located on West Florissant Avenue where many of the protests have taken place.

The restaurant has boarded up its windows but written in large letters in red paint on the plywood planks is the promise: "We will be back!!!" and workers were selling sandwiches in the parking lot next to an outdoor meat smoker.

"We are seeing the judicial process beginning," said Harris, who works as a youth counselor in St. Louis. "Voices are actually being heard."

Ferguson is predominantly black, but its police force, political leadership and public education administration are dominated by whites. Activists and demonstrators have complained that Brown's death was the culmination of years of unfair police targeting of blacks.

In Washington, Missouri Senator Claire McCaskill announced she would lead a Senate hearing next month to look at the militarization of local police departments.

A US military program that sends armored cars, camouflage and other battlefield equipment to police departments has come under scrutiny as the protesters in Ferguson have been met by heavily armed police clad in body armor and driving heavy armored vehicles.

US Attorney General Eric Holder has said such displays should stop. "At a time when we must seek to rebuild trust between law enforcement and the local community, I am deeply concerned that the deployment of military equipment and vehicles sends a conflicting message," Holder said last week.

A grand jury met on Wednesday to begin hearing evidence in the Brown case. That process could take into October before the panel releases its findings, said St. Louis County Prosecuting Attorney Bob McCulloch.

McCulloch, who is responsible for deciding whether to pursue criminal charges against the police officer, has held the top county prosecutor's job for 23 years and has promised an impartial investigation.

Many Ferguson residents, angry that the police officer in question is not in custody and has gone into hiding, fear that if there is no indictment, more street violence is inevitable.