BATON ROUGE, La. (CBSNewYork/AP) -- The Justice Department says it will open a civil rights investigation into the videotaped police shooting of a black man outside a Baton Rouge convenience store.
Agency spokesman David Jacobs said Wednesday that the FBI's New Orleans Division and the U.S. attorney's office will participate in the investigation of the fatal shooting of 37-year-old Alton Sterling.
Police say they went to the store Tuesday after an anonymous caller said Sterling had threatened someone with a gun.
"This incident is going to be investigated impartially, professionally and thoroughly by the United States Department of Justice Civil Rights Division," said Louisiana Gov. John Bel Edwards. "I have very serious concerns. The video is disturbing, to say the least."
As CBS News' David Begnaud reported, cell phone video shows officers struggling with Sterling outside the convenience store. During the confrontation someone screams he's got a gun.
Seconds later, shots were fired. Sterling was pronounced dead at the scene.
Baton Rouge's police chief says Sterling was armed but there are still questions about what happened.
Chief Carl Dabadie Jr. called the shooting a tragedy during a news conference and said: "Like you, there is a lot that we do not understand. And at this point, like you, I am demanding answers."
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.
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. Many federal probes conclude without criminal charges.
The crowd that gathered late Tuesday afternoon at the store where Sterling died grew to more than 200 people. They chanted "black lives matter" and "hands up don't shoot" and waved signs late into the night.
An online video that surfaced purporting to show the killing of Sterling added to protesters' outrage. The protest lasted into the night, with people chanting and holding up signs. The Associated Press has not been able to authenticate the video.
"Mr. Sterling was not reaching for a weapon. He looks like a man that was actually fighting for his life," said state Rep. Edmond Jordan, an attorney for Sterling's family.
An autopsy shows Sterling died of multiple gunshot wounds to the chest and back, East Baton Rouge Parish Coroner Dr. William Clark said.
Officers responded to the store about 12:35 a.m. Tuesday after an anonymous caller indicated a man selling music CDs and wearing a red shirt threatened him with a gun, Cpl. L'Jean McKneely said.
Two officers responded and had some type of altercation with the man and one officer fatally shot the suspect, McKneely said. Police have identified the officers involved as Blaine Salamoni and Howie Lake II.
Both officers have been placed on administrative leave, which is standard department policy, he said.
The store's owner, Abdul Muflahi, told CBS Baton Rouge affiliate 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 of him, the first officer shot him "four to six times."
The owner said 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.
WAFB-TV posted video of the shooting on its website with a warning saying "SOME MAY FIND THE VIDEO DISTURBING AND GRAPHIC."
McKneely said late Tuesday that he could not confirm Muflahi's description of the event or any other details of the investigation.
The 37-year-old's family, and community leaders have called it murder.
"My brother didn't deserve it. He didn't deserve it at all," said Sterling's sister Mignon Chambers. "Just to open fire, that's not the answer. That was a life that you took away. That was a family member."
"The worries are that we are not going to get the information that we need to cool this situation down and this may definitely be the next Ferguson right here in Baton Rouge, that's the worry," said community activist Silky Slim.
Sterling's son broke down as the teen's mother addressed the media.
"One of the greatest fears is to see your child hurt, and know there was nothing you can do," Quinyetta McMillon said.
Kimberly Lang said she purchased CDs from Sterling on occasion and said he did not have a reputation for violence, according to a report by NOLA.com/The Times-Picayune. If Sterling did have a gun on him, Lang said, it was probably because he feared being robbed while peddling his CDs late at night, not because he wanted to threaten anyone.
The Rev. Jesse Jackson called the shooting a "legal lynching," adding that he is "outraged."
A vigil was held outside Wednesday night outside the store where Sterling was gunned down, and protests were held in many parts of the country. In Philadelphia, demonstrators marched up and down the streets of Center City canting, "No justice, no peace," CBS Philly reported.
"It's just enough. This is enough. What do we do at this point now? They're killing us," Rennie Robinson said in Philadelphia. "They're out here actually killing us."
The shooting has sparked protests across Baton Rogue with the head of the local NAACP calling for the police chief to be fired, but today the chief said he has no plans of leaving.
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