(CNN) -- A federal judge Wednesday sentenced five former New Orleans police officers to prison terms ranging from six to 65 years for the shootings of unarmed civilians in the chaotic aftermath of Hurricane Katrina, prosecutors said.
The shootings occurred on the Danziger Bridge on September 4, 2005, six days after much of New Orleans went underwater when the powerful hurricane slammed into the Gulf Coast. The ex-officers were convicted in August on a combined 25 counts of civil rights violations.
U.S. District Judge Kurt Engelhardt imposed the stiffest sentence on former officer Robert Faulcon, who was handed a 65-year term for his involvement in shooting two of the victims. Former sergeants Kenneth Bowen and Robert Gisevius got 40 years for their roles in the incident, while ex-officer Robert Villavaso was sentenced to 38 years.
The lightest term went to former detective sergeant Arthur Kaufman, who was sentenced to six years for attempting to cover up what the officers had done, according to the U.S. attorney's office in New Orleans.
The men were accused of opening fire on an unarmed family, killing 17-year-old James Brissette and wounding four others. Minutes later, Faulcon shot and killed Ronald Madison, a 40-year-old man described by Justice Department officials as having severe mental disabilities and who was trying to flee the scene when he was shot, according to the Justice Department.
At the time, New Orleans police said they got into a running gun battle with several people. Prosecutors said Kaufman wrote the department's formal report on the incident, which concluded the shootings were justified and recommended the prosecution of two of the survivors "on the basis of false evidence."
During the trial, the defense asked the jury to consider the stressful circumstances the officers were operating under following Katrina. The shootings took place during a week of dire flooding, rampant looting and death by drowning, and police were strained by suicides and desertion among their ranks.
But U.S. Attorney Jim Letten said the prison sentences send the message that "when the crisis we face is the most threatening, that when the challenges are the greatest, the rules don't go out the window."
"In fact, that's when the discipline, when the honesty of our public servants, our police and the men and women of law enforcement are most critical," Letten said.
Romell Madison, brother of victim Ronald Madison, told reporters after Wednesday's proceedings that his family was happy with the sentences, even though prosecutors had to enter into plea agreements with several other officers to obtain the convictions.
"I think it made a big difference, even though they did give them lower sentences, that they did come forth and testify to get the truth out," Madison said. "At least we got to the truth."
Five other officers, including a lieutenant, have already pleaded guilty and been sentenced to prison terms of up to eight years in the case for conspiracy and obstruction of justice. Letten said the plea deals were necessary to break a "logjam" that had prevented investigators to get the whole story of what happened on the Danziger Bridge, in New Orleans East.
The Justice Department brought charges after a similar case brought by local prosecutors foundered. Thomas Perez, the head of the department's civil rights division, said the feds inherited a "cold case" when they took over in 2008.
"There were many, many New Orleans police officers who performed courageous, selfless acts of heroism in the aftermath of Hurricane Katrina," Perez said. "But regrettably, the acts of heroism of so many have been overshadowed by the misconduct of a few.
"What we learned in this trial -- what we learned in these convictions -- is that the Constitution never takes a holiday. The Constitution applies every day of every week, and no police officer can take it upon himself or herself to suspend the Constitution."
In 2010, three former officers were convicted in the case of 31-year-old Henry Glover, who was shot to death and his body burned. David Warren, the officer convicted of shooting Glover in the back, was sentenced to more than 25 years in prison in 2011; Gregory McRae, who was found guilty of burning the body, received a 17-plus-year term. A federal judge has ordered a new trial for the third, Lt. Travis McCabe, who was accused of obstructing the investigation.
The Justice Department's Civil Rights Division launched an investigation into what it called "patterns or practices" of alleged misconduct by New Orleans police in the aftermath of Katrina, which killed nearly 1,500 people in Louisiana and more than 1,700 across the Gulf Coast.
Police Superintendent Ronal Serpas said Wednesday that his department "will continue to take bold and decisive actions to right the wrongs inside the department, some of which we now know go back seven full years."
Mary Howell, a lawyer for the Madison family, said those promised reforms are "the most critical part in all of this."
"This just can't ever happen again," she said.
Lance Madison, who was with his brother on the bridge that September day, told reporters that he is grateful that his brother had received justice. But he added, "I try to avoid the Danzinger Bridge, because when I go there, it just brings back memories of what I went through."
CNN's Matt Smith contributed to this report.