(CNN) A second video showing the shooting death of Alton Sterling, a black man shot several times while being held on the ground by police outside a Louisiana convenience store, was posted online Wednesday as federal authorities took charge of the investigation and local officials asked residents to keep their protests peaceful.

The video, obtained by CNN, shows another angle and was recorded closer to the shooting by one of two white Baton Rouge police officers who were answering a 911 report of a man with a gun. It is the second of two bystander videos that show the encounter. One posted online Tuesday night quickly sparked local protests and drew national attention.

In the new 38-second recording, Sterling is already on the ground, on his back. One officer is kneeling to Sterling's left. The other officer appears to be straddling Sterling's legs. Sterling can be seen from the chest up and his lower legs are also visible. His left arms and hands are not visible; his right arm is by his side.

After gunshots are heard, the camera pans to the right then back to Sterling, who has a large blood stain on his chest. The officer who was on his legs now lies on the pavement above Sterling's head, his gun pointed.

The officer radios for an ambulance. As Sterling moves his left arm toward his face and then his chest, the other officer appears to remove something from one of Sterling's right pockets. Baton Rouge Police Chief Carl Dabadie Jr. said Sterling was armed at the time he was killed and one witness said the officer removed a gun from Sterling's pocket.

Sterling, a 37-year-old man who sold CDs and DVDs outside the store, died of his wounds. The officers involved in Tuesday's shooting -- Blane Salamoni and Howie Lake II -- have been placed on administrative leave. A source close to the investigation told CNN the officers were interviewed Tuesday night.

Officials pledge transparency

The second video emerged on a day in which Baton Rouge and Louisiana officials said the investigation into Sterling's shooting would be led by federal authorities.

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The revelation also came as a vigil for Sterling was held outside the convenience store and city officials met with residents of Baton Rouge.

The U.S. Justice Department's Civil Rights Division is leading an investigation into what happened. The U.S. attorney's office in Baton Rouge, the FBI and state police also will be involved in the investigation, Gov. John Bel Edwards said.

Tensions are running high in the city of 238,000 people as officials vowed to be transparent about how they handle the controversial case that has sparked vigils in cities around the country.

Searching for answers

Edmond Jordan, an attorney representing Sterling's family, said the first video of the shooting raises troubling questions.

"I think that the city is going to have to give us some good answers," Jordan, who is a Louisiana state legislator, told CNN. "And I don't know if they'll be able to."

Quinyetta McMillon, the mother of one of Sterling's children, teared up as she discussed the first shooting video. Her 15-year-old son stood beside her, sobbing.

JUST WATCHED Family of Alton Sterling breaks down at conference Replay More Videos ... MUST WATCH Family of Alton Sterling breaks down at conference 02:45

"The individuals involved in his murder took away a man with children who depended upon their daddy on a daily basis. ... As this video has been shared across the world, you will see with your own eyes how he was handled unjustly and killed without regard for the lives that he helped raise," she said.

McMillon vowed to join fellow citizens of Baton Rouge in making sure those responsible are held accountable.

"I, for one, will not rest," she said, "and will not allow y'all to sweep him in the dirt."

A police incident report says Sterling was shot by one of the officers, but doesn't specify which.

Edwards called for calm and unity, saying he has "very serious concerns" after watching the video.

"The video is disturbing to say the least," he said.

The first video

At 48 seconds, the first video is longer and begins with the camera facing a car dashboard as the three men stand near the vehicle. A single pop is heard. Then someone yells, "Get on the ground."

Another pop follows.

The camera then pans up to two officers confronting a man in a red shirt. The man is Sterling, according to his family's attorney.

Still frames from the video that appears to show Alton Sterling being shot to death.

An officer pulls him over the hood of a silver car and pins him to the ground. Once he's down, the officer begins to assist a second officer in restraining Sterling.

Seconds later, someone shouts, "He's got a gun."

An officer can be seen drawing something from his waist and pointing it at the man on the ground.

More yelling follows, though it's hard to make out what's being said. Then there are two bangs.

The witnesses inside the car shout and swear. Three more bangs go off. A woman in the car starts crying.

More witnesses?

Investigators said they'll review multiple videos of the shooting, and they're canvassing for witnesses.

"If you have any information, we urge you to come forward," the police chief said Wednesday.

The owner of the convenience store where Sterling was killed said he's sure the shooting was caught on his store's surveillance cameras, though he hasn't seen it. Police took the video later Tuesday, he told CNN.

There also is police body camera footage of the shooting of Sterling -- even though the cameras were dislodged -- Baton Rouge police Lt. Johnny Dunham told reporters. The cameras continued to record, he added.

"That footage may not be as good as we hoped for," Dunham said.

Authorities haven't said what those police videos or other surveillance footage of the scene show.

A source involved in the investigation told CNN that none of it is nearly as clear as two bystander videos. The source also told CNN the witness who called 911 said Sterling was "brandishing a gun," not pointing it at someone.

The 'CD man'

Sterling was known as the "CD man," a laid-back guy who would sell tunes and DVDs outside the convenience store where he was shot, according to local media.

"Alton was a respected man. He was beloved in the community. He did not deserve the treatment and this excessive force that was exerted on him by the police department," Jordan, his attorney, told CNN.

Now Sterling's family is "grieving and mourning for an unnecessary loss of life," the attorney said.

"Alton was out there selling CDs, trying to make a living. He was doing it with the permission of the store owner, so he wasn't trespassing or anything like that. He wasn't involved in any criminal conduct," Jordan said.

Abdullah Muflahi, the owner of the Triple S Food Mart, said he saw the officers slam Sterling on a car.

"They told him not to move," he said. "He was asking them what he did wrong."

He said the officers then used a Taser on Sterling at least once before shooting.

Both got on top of him, and one ordered him not to move, Muflahi said.

The one closest to Sterling's legs yelled "gun," he said, and the shots followed.

Just five minutes before, he walked into the store getting something to drink, joking around, (and we were) calling each other names. Abdullah Muflahi, owner of the Triple S Food Mart in Baton Rouge

After the shooting, Muflahi said an officer reached into Sterling's pocket and pulled out a gun.

Muflahi said he'd known Sterling for six years and never saw a confrontation between Sterling and anyone. Sterling never got into fights, he said. And the store owner said he wasn't aware of any incident Tuesday that would have spurred a 911 call.

"Just five minutes before," Muflahi said, "he walked into the store getting something to drink, joking around, (and we were) calling each other names."

Later, Muflahi said he didn't hear Sterling say anything after the initial confrontation.

"(Sterling) was really confused," Muflahi said. "He didn't know what was going on or why they were there."

He said Sterling never showed a weapon.

"The gun was never anywhere in his hand, nor his hand wasn't near, inside his pocket," he said.

Sterling has had encounters with law enforcement before.

In 2009, he was charged with carrying a weapon (a firearm) while in possession of a controlled substance (marijuana). He pleaded guilty two years later and was sentenced to five years in prison, with credit for time served and a recommendation of work release and drug treatment. Sterling had pleaded guilty to other charges in the past.

There's no evidence that officers who responded to the convenience store early Tuesday were aware of his criminal history.

Cause of death: 'Multiple gunshot wounds'

A preliminary autopsy found Sterling's cause of death was from "multiple gunshot wounds to the chest and back," East Baton Rouge Parish Coroner William "Beau" Clark said.

He declined to provide additional details about how many gunshot wounds Sterling sustained.

A full autopsy will be completed over the next 60 to 90 days, Clark said, pending toxicology results.

Salamoni and Lake, the officers involved, were placed on administrative leave Tuesday morning, police said.

Salamoni is a four-year veteran of the department. Lake has been with the force three years.

'He was handled unjustly'

At a news conference, the president of the NAACP branch in Baton Rouge called for the police chief and mayor to resign in the wake of the shooting.

"We're actually here today to speak to the culture of the Baton Rouge Police Department. This incident is only one incident in many," Michael McClanahan told reporters. "What we're going to do is root out the 1% of bad police officers that go around being the judge, the jury and executioner of innocent people, period, but more specifically, innocent black lives."

The officers involved should be held accountable, McClanahan said.

"I'm calling on anybody in this city with any backbone to go and arrest those two officers," he said. "If the system will work for anybody, let it work for them, too."

"I don't plan on resigning," police Chief Carl Dabadie Jr. said. "We have done a lot of good in this community. We have worked very hard in this community. Do we have an issue right now? Yes. But we are working right now to bring the truth out."

'We ain't running from this'

People gathered Wednesday night at the site of the shooting to hold a vigil for Sterling.

Aaron Banks, lifelong Baton Rouge resident, was there.

"I'm feeling all sorts of emotions from this crime," he said.

Earlier, protesters took to the streets near where Sterling was killed after news of his death spread.

Members of Sterling's family were among them, Jordan said.

"Pretty much everybody who knows him knows he's a sweet person," his sister, Mignon Chambers, told CNN affiliate WVLA-TV

"It wasn't right, and something needs to be done."

The protests were largely peaceful, according to local media.

Some streets were shut down, a few individuals spoke and those on the scene mostly played music and chanted.

"We ain't running from this," one man could be heard telling the crowd. "We gonna pray first, but we gonna stand tonight. We gonna stand tomorrow. And we gonna stand as a community."