In a confrontation partially captured yesterday on videotape, officerswho was swinging a knife.
The shooting was the first involving police since New Orleans reopened after Hurricane Katrina.
A police spokesman is defending the officers' response, saying they were "fearing for their life." But a bystander who saw part of the confrontation says it didn't seem like anyone was going to get hurt.
The shooting comes after a videotapedled to two firings. There also have been allegations of theft and looting by officers in the days after the hurricane.
Now, the city's embattled police department will have another internal investigation to face.
A police spokesman said the officers who fired on the man Monday will be reassigned pending the outcome of the probe, but he defended their response, saying at least one officer's life was in danger just prior to the barrage of gunfire.
"You have a subject who's lunging at them with a knife... swinging wildly at them and they're fearing for their life," said Officer David Adams, a police spokesman. "They had no other choice but to resort to lethal force."
Adams said police fired several shots at the man, but would not disclose how many officers were involved in the shooting, New Orleans CBS Affiliate WWL reports.
Officers repeatedly asked the man to drop the knife and used pepper spray to try to subdue him, but he used a cloth to cover his face and was still able to walk toward an officer and threaten him, authorities said.
"Evidently the pepper spray had no effect," Adams said.
The shooting occurred on St. Charles Avenue, a prominent important thoroughfare in the city, famous for its historic green street cars and Mardi Gras parades.
Witnesses said a half dozen or more shots were fired.
Phin Percy videotaped a portion of the incident from his father's second-story apartment. "The cops kept telling him, 'Lay down! Lay down!' This went on for about three minutes," he said.
Percy told CBS News correspondent Trish Regan that from everything he had witnessed leading up to the shooting, he thought it was justified.
"This man was threatening the officers," he said. "He wouldn't listen to the simple commands of putting the knife down and laying on the ground."
Trey Brokaw, a patron at a nearby bar, said he saw the victim with a knife in his hand shortly before the shooting. "I didn't see anyone near him," Brokaw said. "It didn't seem like anyone was going to get hurt to me."
Brokaw said he did not see what happened in the final moments before the shots rang out.
The victim's name was not released because his family had not been notified.
It was the first shooting of any kind involving a New Orleans officer since the city was officially reopened after Hurricane Katrina damaged many neighborhoods and displaced tens of thousands of residents nearly four months ago, Adams said.
Since the storm, the police department has struggled to rebuild its ranks and address questions about officers' conduct.
Hundreds of police left the city without permission in the days after the storm. There were also allegations of theft and looting by officers, and the videotaped beating of a retired teacher by police in the French Quarter. The police chief resigned a month after the storm.
Two of the officers accused of the beating were fired; a third was suspended for 120 days. All three are scheduled to be tried next month. The allegations of looting and theft are being investigated.