By Bryn Stole and Kathy Finn

BATON ROUGE, La. (Reuters) - The U.S. Justice Department said on Wednesday it would investigate the killing of a black man pinned to the ground and shot in the chest by two white police officers outside a convenience store in Baton Rouge, Louisiana.

Captured on at least two videos, graphic images of the shooting of Alton Sterling, 37, early Tuesday morning stirred protests and social media outcry over the latest case of alleged police brutality against African-Americans in cities from Ferguson, Missouri, to Baltimore and New York.

One of the two officers shot Sterling five times at close range, and the other removed something from Sterling's pants pocket as he was dying, according to images on a video recorded by Abdullah Muflahi, owner of the Triple S Food Mart where Sterling was killed in the parking lot.

"I'm heartbroken. It's outrageous. It's crazy," said Muflahi, who considered Sterling a friend and allowed him to sell CDs outside his store. He provided a copy of the video to Reuters and said police took a gun from Sterling's pocket.

Several hundred people gathered on Wednesday for a prayer vigil near the spot where Sterling was fatally shot, with speakers calling for peaceful protests, justice and unity in the face of "excessive force" by police against black residents.

"If we stand divided, we are already defeated," Bishop Gregory Cooper of Baton Rouge told the crowd, which included families with children and filled the store's parking lot as well as nearby streets. Police stayed on the fringes of the gathering.

Local officials rushed to defuse tensions, saying there would be an independent investigation, after media showed a separate graphic video of the shooting recorded by a bystander.

"I have very serious concerns. The video is disturbing, to say the least," Governor John Bel Edwards told reporters.

Baton Rouge Mayor-President Kip Holden and local police said they welcomed the probe launched by the Justice Department, the Federal Bureau of Investigation and federal prosecutors.

Presumptive Democratic presidential nominee Hillary Clinton said incidents like this one undermine trust between police and the communities they serve.

"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 in a statement.

There was no immediate statement on the incident from presumptive Republican nominee Donald Trump.

"HE'S GOT A GUN"

A video recorded on the bystander's cell phone shows an officer confronting Sterling in the store's parking lot and ordering him to get on the ground. The two officers then tackle Sterling to the pavement, with one pulling a gun from his holster and pointing it at Sterling's chest.

Muflahi's video shows the officers on top of Sterling. One of them yells "he's got a gun." The video jerks away from the scene after the first two shots are fired. Three more shots are heard, then the camera shows one of the officers leaning over Sterling and taking something out of his pocket.

Police did not say how many shots were fired and declined to say whether a stun gun was used on Sterling. Muflahi said police Tasered Sterling before he was tackled.

The two police officers involved in the shooting, Blane Salamoni, a four-year veteran, and Howie Lake, a three-year veteran, were both put on administrative leave, Baton Rouge Police Chief Carl Dabadie said at a news conference.

The officers were responding to a call regarding a black man who reportedly made threats with a gun, Dabadie said.

"When officers arrived Sterling was armed and the altercation ensued that resulted in the loss of his life," Dabadie said.

The body cameras of both officers became dislodged during the altercation, but continued recording audio and video, police said. Those and other recordings will be turned over to federal investigators, police spokesman Lieutenant Johnny Dunham told reporters.

RAP SHEET

According to court records, Sterling had multiple criminal convictions since the mid-1990s, for battery, resisting arrest, burglary and other crimes. He was a registered sex offender after spending close to four years in prison for felony carnal knowledge of a juvenile.

Relatives of Sterling and acquaintances from the neighborhood described him as a local fixture who had peddled copied CDs, DVDs and games in front of the Triple S Food Mart for years.

Those who knew Sterling described a funny, jovial and friendly person.

Cameron Sterling, Alton's 15-year-old son, broke down crying at a news conference on Wednesday morning as his mother spoke. "He was killed unjustly and without regard for the lives he helped raise," said the mother, who did not give her name.

(Additional reporting by Letitia Stein in Tampa, Fla., Laila Kearney in New York, Brendan O'Brien in Milwaukee and Jon Herskovitz in Austin, Texas; Writing by Fiona Ortiz and Colleen Jenkins; Editing by Matthew Lewis and Leslie Adler)