FERGUSON, Mo. — As demonstrators gathered for the fourth straight day Tuesday, the Ferguson, Missouri, Mo., police chief said that because of death threats he will not publicly release the name of the police officer who fatally shot an unarmed black teenager whose killing has roiled racial tensions in the St. Louis suburb.

The parents of Michael Brown, 18, who was shot multiple times Saturday during a street confrontation with a Ferguson police officer, have called on authorities to release the name of the officer and prosecute him. Local law enforcement authorities and the Justice Department have launched parallel investigations into the shooting.

On Monday, Ferguson Police Chief Thomas Jackson said he would reveal the identity of the officer by noon Tuesday. But after threats were made to the police department and on social media, a spokesman for the department said it is not safe at this time to release the officer’s name.

The announcement comes after another night of unrest Monday, albeit smaller than the previous night, when vandals broke windows, looted and damaged 12 businesses in Ferguson.

In Monday night’s standoff, police in riot gear fired tear gas into crowds of protesters and arrested up to 15 people.

The heated protests in part have reflected the racial divisions in Ferguson, population 21,000, where two-thirds of residents are black but police and city officials are predominantly white. Black leaders have called for nonviolent demonstrations to address racism in the Ferguson and greater St. Louis police departments.

“The unrest that has taken place in the wake of Mr. Brown’s death at the hands of police is the unfortunate result of the understandable pain and frustration felt by that community,” said Sherrilyn Ifill, president and director-counsel of the NAACP Legal Defense & Education Fund Inc. “That pain and frustration are mirrored in communities across this country where unarmed black teens and adults have been killed by police and civilians. These feelings must be met with proactive efforts to address to what is clearly a deeply flawed system of police and civilian responses to perceived black criminality.”

On Monday the Justice Department announced an investigation in conjunction with the separate county police inquiry.