Baton Rouge community leaders on Thursday demanded a broad criminal investigation of two white police officers involved in the fatal shooting of a black man in Louisiana's capital in one of the mounting number of deadly encounters between U.S. law enforcement and black suspects.

Representatives from the community organization Together Baton Rouge urged authorities to consider all possible federal and state criminal charges against officers Blane Salamoni and Howie Lake in the death of Alton Sterling, 37, on Tuesday.

The 300-pound (136-kg) Sterling was pinned to the ground and fatally shot in the chest outside a convenience store after the officers responded to what police said was a call about a black man reported to have made threats with a gun.

"We don't want this to be a narrow investigation," Edgar Cage, a spokesman for the group, said at a Baton Rouge church. "We plan to use this tragic event as a tool, a stimulant to change the culture."

The U.S. Justice Department on Wednesday said it would conduct a civil rights investigation into Sterling's killing. The city's mayor and police chief welcomed the move, but community leaders said they worried the probe would be too limited.

Citing an unnamed law enforcement official, CNN reported on Thursday that a homeless man placed the 911 call after seeking money from Sterling, who was selling CDs outside the store.

Sterling showed the man his gun and said to leave him alone, the official told CNN. Reuters could not independently confirm that account with Baton Rouge police spokesmen, who did not respond to a request for comment.

Sterling, a father of five, had several criminal convictions since the mid-1990s for battery, resisting arrest, burglary and other crimes. He was a registered sex offender after spending nearly four years in prison on a charge that he had sex with a 14-year-old girl when he was 20.

PRAYER FOR SHOOTING VICTIMS

Together Baton Rouge began its news conference with a prayer dedicated to Sterling and Philando Castile, a black man shot and killed by a police officer during a traffic stop on Wednesday near Minneapolis.

The shootings and videos showing their bloody aftermath have sparked protests, including an overnight rally in Baton Rouge that drew about 300 people who stood in a peaceful vigil near the Triple S Food Mart where Sterling was killed.

Video recorded by a bystander's cellphone showed an officer confronting Sterling and ordering him to the ground. The two officers then tackled him to the pavement, with one pulling a gun from his holster and pointing it at Sterling's chest.

One officer shot Sterling five times at close range, and the other took something from his pants pocket as he was dying, another video recorded by Abdullah Muflahi, owner of the store where Sterling was killed in the parking lot, showed.

Police said Sterling was armed. Muflahi said in an interview that police took a gun out of Sterling's pocket after shooting him.

Officers Salamoni and Lake have been put on administrative leave, police said.

The deaths of Sterling and Castile are the latest in a string of incidents in recent years involving police treatment of black men and boys in cities including Baltimore, Chicago, New York, Cleveland, Tulsa, Oklahoma and North Charleston, South Carolina.

In Baton Rouge, where people marched, sang, chanted and at times blocked traffic, protesters accused police of using excessive force against black residents.

"There is not going to be a riot until they show they are not going to prosecute these people," said Arsby, a 53-year-old truck driver who declined to give his last name, as he stood outside the store where Sterling was shot. "Right now it's just started."

(Additional reporting by Brendan O'Brien, Kathy Finn and Bryn Stole; Writing by Colleen Jenkins; Editing by Will Dunham)