Louisiana Gov. John Bel Edwards, calling the cellphone video of the fatal shooting of a black man by two Baton Rouge police officers "disturbing," announced Wednesday that the U.S. Justice Department will lead the investigation of the killing with the help of the FBI and state police.

He told reporters that the inquiry, originally in the hands of local police, would be handled "impartially, professionally and thoroughly." He said the agency's civil rights division would be in charge of the probe.

"I have very serious concerns. The video is disturbing to say the least," Edwards said.

The move came only hours after leaders of Baton Rouge's black community joined family members of the victim, Alton Sterling, 37, at a news conference to to call for more protests and for the inquiry to be turned over to state and federal authorities.

The governor also said he had spoken with Sterling's aunt, Sandra Sterling, to express his condolences.

Sandra Sterling had joined community leaders in front of city hall earlier to call her nephew's shooting a "horrible thing." "He didn’t deserve that," she said.

The governor called on the Baton Rouge community and faith-based leaders "to work with all of us that we remain calm and peaceful as the details unfold."

The Justice Department’s investigation will look into whether the officers willfully violated Sterling’s civil rights through the use of unreasonable or excessive force, the Associated Press reported. Similar investigations, which often take many months to resolve, were opened following the deaths of Michael Brown in Ferguson, Missouri, and Eric Garner in New York.

Federal investigators must meet a high legal burden to bring a civil rights prosecution, establishing that an officer knowingly used unreasonable force under the circumstances and did not simply make a mistake or use poor judgment, AP reported. Many federal probes conclude without criminal charges.

Protests erupted late Tuesday and continued into the early morning hours following the appearance on Facebook of the graphic video purportedly showing the shooting.

The two officers, who have not been identified, have been placed on administrative leave pending an investigation.

The officers arrived at the Triple S Food Mart about 12:35 a.m. Tuesday after an anonymous caller indicated a man, later identified as Sterling, selling music CDs and wearing a red shirt threatened him with a gun, Cpl. L’Jean McKneely said.

Mufleh Alatiyat, a 25-year-old employee of the store described Sterling as generous and said he often gave away CDs or petty cash or bought food or drink for some people. “He was a very nice guy,” he said. “He helped a lot of people.”

The 48-second cellphone video captured by a bystander shows an officer firing at least one round into Sterling's chest followed by the sound of at least four shots as the camera abruptly turns away.

"Get on the ground, get on the ground!" one officer shouts at the outset of the video clip.

One officer pulls down and pins the man's left arm. His right arm is not visible in the video.

"He's got a gun! Gun," one officer says, prompting the officer visible in the video to draw his weapon and point it at the man's chest. That action is followed by a flash from the gun.

An autopsy shows Sterling died of multiple gunshot wounds to the chest and back, according to East Baton Rouge Parish Coroner William "Beau" Clark.

The owner of the convenience store, Abdul Muflahi, told WAFB-TV that the first officer used a stun gun on Sterling and the second officer tackled the man. Muflahi said as Sterling fought to get the officer off him, the first officer shot him “four to six times.”

He says Sterling did not have a gun in his hand at the time but he saw officers remove a gun from Sterling’s pocket after the shooting. Police confiscated a video of the incident taken by the store's surveillance cameras.

Rep. Cedric Richmond, D-La., called for the Department of Justice to investigate the killing. He said officials claimed that both officers had body cameras "but they fell off during the struggle and do not show the shooting."

By dawn Wednesday, protesters and friends had created a makeshift memorial to Sterling on the white folding tables and fold-out chair he used to sell homemade music compilations on CD’s.

The protests increased after the video surfaced, with demonstrators chanting, "hands up, don't shoot" and "black lives matter."

Demonstrators blocked the intersection near the convenience store before 10 p.m. CT Tuesday night. They eventually cleared the streets and moved to the sidewalks.

Michael McClanahan, president of the Baton Rouge NAACP, call on the mayor to fire the chief of police and then resign himself. He also called for the probe into the killing to be handed over the the Louisiana State Police.

"The best way to insure that this is no cover up is to turn it over to a neutral third party," McClanahan said.

He said the community's goal was to "root out the 1% of the bad police who believe they are the judge, jury and executioner of innocent people, period, but most of all black lives."

McClanahan called on the Baton Rouge police to arrest the two officers. "If the system works for anyone, it should work for them, too," he said.

Gary Chambers, publisher of The Rouge Collection, which serves the predominantly black community of north Baton Rouge, called for a community meeting Wednesday evening of blacks, whites, other ethnics groups and faith-based leaders to "come together as a city and say that this is not going to stand in this community."

"This is not a place of division," Chambers said. "This is not a community place where we are trying to pit all of our community against all police. We understand that not all police are bad, but this must be answered for."

Quinyetta McMillon, mother of the oldest of Sterling's five children, broke down repeatedly as she addressed the news conference, At one point her son, who stood next to hear, broke into sobs and buried his face against her arm, and was gently taken by bystanders.

"The individuals involved in this murder took away a man with children who depended on their daddy on a daily basis," she said.

She said the community had come together "to ensure that this event will not go unnoticed, especially for the future."

"I for one will not rest and will not allow him to be swept into the dirt," she said.