The Federal Bureau of Investigation said Monday it is looking for witnesses to the police shooting of an 18-year old black student who was fatally shot in Ferguson, Missouri, as part of its ongoing investigation into an event that has led to a week of racial tension and protests.

The Justice Department has said it would conduct its own parallel investigation of the shooting, which was welcomed by many who said the mostly white Ferguson Police Department cannot be trusted to run the investigation on its own.

People protest Sunday, Aug. 17, 2014, for Michael Brown, who was killed by a police officer last Saturday in Ferguson, Mo. As night fell Sunday in Ferguson, another peaceful protest quickly deteriorated after marchers pushed toward one end of a street. Police attempted to push them back by firing tear gas and shouting over a bullhorn that the protest was no longer peaceful. (AP Photo/Charlie Riedel)

Monday morning, the department said the FBI and Justice Department lawyers have conducted several interviews of witness who were nearby when the shooting occurred.

“Over the next several days, teams of FBI agents will be canvassing the neighborhood where the shooting took place to identify any individuals who may have information related to the shooting and have not yet come forward,” they said. “We ask for the public’s cooperation and patience, and again urge anyone with information related to the shooting to contact the FBI.”

“The FBI can be reached at (800) CALL-FBI, option 4,” they added.

The statement was released by FBI Special Agent in Charge William Woods, U.S. Attorney for the Eastern District of Missouri Richard Callahan, and Acting Assistant Attorney General for the Civil Rights Division Molly Moran.

Over the weekend, the Justice Department said it would conduct another autopsy of Michael Brown, the 18-year old black student who was shot. Justice Spokesman Brian Fallon said the “extraordinary circumstances” involved in the case demand another autopsy.

Fallon said Justice would still consider the state-run autopsy into account in its investigation.

A private autopsy released over the weekend, conducted at the request of Brown’s family, said Brown was shot six times, twice in the head.

In the meantime, protestors and police have continued to clash at night in Ferguson, which prompted Missouir Gov. Jay Nixon (D) to call in the National Guard to restore order in the streets.

The police’s reaction to the protests has prompted another wave of criticism from both Republicans that the police are too heavily armed, and are being overly aggressive in detaining citizens and reporters. One Democrat, Rep. Hank Johnson (D-Ga.), said he would introduce new legislation in September that would limit the types of military-grade weapons that police officers can use.