A New Orleans police officer who killed an unarmed man during a police shooting after Hurricane Katrina told a jury on Wednesday he felt "indescribable fear" in the moments before the shooting.

Robert Faulcon, testifying in the trial of five officers accused in the 2005 shooting, admitted he fired the shotgun that killed Ronald Madison, a 40-year-old man with a mental disability, even though Madison had not fired at him.

James Brissette, 17, was also killed during the shooting and four other civilians were seriously wounded.

Faulcon said he had seen civilians with guns when he first arrived at the bridge, and he believed his life was in danger.

"I became paralyzed with fear, really, that we were going to be shot at," he said.

Faulcon is the first defendant to take the stand in the trial of five officers charged with civil rights violations in connection with the shooting, which took place when much of New Orleans was still underwater, and an alleged cover-up.

Also on trial are officers Kenneth Bowen, Robert Gisevius, Anthony Villavaso and Arthur Kaufman.

The shooting occurred when a dozen officers responded to a radio call that police had been fired on and that the shooters were headed toward the Danziger Bridge. Faulcon was among the officers who jumped into a rental truck and sped to the scene.

"I knew we were going into a bad situation. I just expected to be shot at," he said.

Mike Hunter, who drove the truck that day and is among five officers who have pleaded guilty to a role in the incident, testified previously that he fired a series of "warning shots" into the air as the truck arrived at the bridge.

Faulcon, who rode in the back of the truck, said when he heard the initial shots he couldn't tell where they were coming from. When he jumped to the ground he caught sight of two people with handguns, he said, and that's when he first fired his Mossberg shotgun.

"I feel horrible," he said. "When I saw guns, I might have been right and I might have been wrong, but I wouldn't have shot at unarmed people."

Under questioning by defense lawyer Lindsay Larson, Faulcon said he had no role in preparing several versions of a report which stated that civilians on the Danziger Bridge had weapons and that officers who shot guns were returning fire.

Poised and respectful through several hours of testimony, Faulcon, who had eight years of active military service before becoming a New Orleans officer in 2000, said he had never fired a weapon in the line of police duty until the day of the bridge incident.

"My heart goes out to the people that were hurt and to the families of the people that were hurt," Faulcon said.

In cross-examining Faulcon, lead prosecutor Barbara Bernstein tried to get him to admit that he fired deliberately at Madison and others even though he knew all the civilians were unarmed.

Faulcon stuck to his position that at the time he believed his life and lives of other officers were in danger.

The devastated, chaotic state of post-Katrina New Orleans was a recurring theme in Faulcon's testimony. He said his wife, who was nine months pregnant, evacuated the city the day before the hurricane to be sure she'd have access to a hospital.

When flood waters began to rise, Faulcon sought safety on an upper floor of a hotel. When water reached the second floor, he had to swim out to reach a rescue boat.

Faulcon said he wore the same water-stained clothes for several days as he helped rescue civilians trapped by the water. More than three weeks passed before he got word that his wife had given birth to their son.

Shortly thereafter, he resigned from the police force and joined his family. They relocated to Houston, where Faulcon became a truck driver.