Protestors gather in front of a mural of Alton Sterling on the wall of a convenience store in Baton Rouge, Louisianna where Sterling was apparently shot dead while being held down by police. — Photo  bangkokpost.com

WASHINGTON — Mourners gathered late Wednesday for a vigil to commemorate a black father of five shot to death by police in Louisiana, hours after federal civil rights investigators said they will probe the incident.

Lighting candles just before dusk, a crowd of hundreds gathered outside the Baton Rouge convenience store where 37-year-old Alton Sterling was shot dead by an officer while already pinned to the ground.

Following the ceremony, people continued to gather at the Triple S Mart store, where a mural of Alton had already been painted on the side of the building, local newspaper The Advocate reported.

Sterling’s death was captured on cell phone video, triggering protests in the city and outrage nationwide over the latest case of alleged police brutality against black suspects.

The shooting came on the eve of a closely watched trial in Baltimore for an officer charged in the death of Freddie Gray, a black man who suffered a broken spine in the back of a police van.

Sterling was fatally shot in the early hours of Tuesday after an anonymous caller told police they had been threatened by a man with a gun, according to the police.

His family’s lawyer said Sterling was merely selling CDs outside a convenience store, with the permission of the shop’s owner.

Officials appealed for calm and promised a transparent investigation.

Calling the video "disturbing," Louisiana Governor John Bel Edwards said federal authorities will take over the investigation, led by the Department of Justice civil rights division.

"I have very serious concerns," Edwards told a news conference in Baton Rouge. "The video is disturbing to say the least."

Edwards said he spoke to the White House and planned to meet with faith-based community leaders to appeal for calm.

Baton Rouge officials identified the officers involved as Blane Salamoni and Howie Lake II. Both were placed on administrative leave, according to procedure, pending the results of the investigation.

’No cover-up’

David Harris, a University of Pittsburgh law professor who studies police behavior and regulation, said it was "unusual for the Department of Justice to step in so quickly."

But he said the opening of a civil rights probe does not necessarily mean the Department will bring a case.

Federal law "requires not only showing of use of force that is excessive, but also that it was a wilful violation of the Constitution," Harris said.

Philip Stinson, a professor in the criminal justice program at Bowling Green State University furthered that "juries don’t like to convict police officers. They give officers every benefit of doubt. These are very hard case to get convictions in."

In Baton Rouge, emotions were running high. At a press conference with relatives of the victim, the head of the city’s chapter of the civil rights group NAACP, Michael McClanahan, called for the resignations of the police chief and mayor.

Both city officials responded with promises of transparency.

"We’re an inclusive city," said Baton Rouge Mayor Kip Holden. "We have a wound right now. But we’ll be healing and making the city and parish whole again."

Police chief Carl Dabadie said he is "demanding answers."

"There is a lot that we do not understand," Dabadie said. "It is our goal and our mission to make sure that a thorough, just, transparent and independent investigation be conducted into this incident."

Democratic presidential candidate Hillary Clinton weighed in as well writing in a statement that Sterling’s death was "a tragedy."

"Something is profoundly wrong when so many Americans have reason to believe that our country doesn’t consider them as precious as others because of the color of their skin," she said.

Video

A graphic video shot by a witness and circulated online showed the altercation between the two officers and Sterling at 12:35 am on Tuesday.

In the video, the officers ordered the tall and heavy-set Sterling to the ground but he remained standing.

The officers wrestled him to the floor, and while he was pinned down one officer pulled a gun and shot Sterling several times at close range.

ABC News published a second witness video on late Wednesday, taken from a different angle, but which did not provide further clarity on the incident. Dabadie said Sterling had been armed.

Suspicion over police actions grew after reports emerged that the officers’ body cameras fell off during the confrontation.

Authorities seized the convenience store’s video surveillance system, which apparently captured the shooting, but have yet to release any footage.

Protesters, including friends and relatives of Sterling, gathered outside the store after the shooting, some blocking roads.

Holding up handmade signs, they chanted: "Black lives matter" and "Hands up, don’t shoot."

Online reactions to the shooting grew on Wednesday.

Actor Jesse Williams, whose televised BET Awards speech about police killings of black people was an Internet sensation, responded on Twitter by asking for "a list of infractions punishable by spontaneous public execution."

African American civil rights leader Jesse Jackson called the shooting "a legal lynching." — AFP