Five ex-New Orleans police officers pleaded guilty on Wednesday to various charges in connection with the killings of two unarmed people in the aftermath of Hurricane Katrina, a federal prosecutor said.

The former officers were convicted in 2011 over an incident in which police fired on unarmed people walking over the city's Danziger Bridge in September 2005. A retrial was later ordered due to prosecutorial misconduct.

They were responding to a report of gunfire after the devastating hurricane flooded the city and triggered looting and other mayhem. In addition to the two people killed, four others were also seriously injured.

Under the plea deal, the four men involved in the shootings - Kenneth Bowen, Robert Faulcon, Robert Gisevius and Anthony Villavaso - pleaded guilty to depriving the victims of their civil rights, obstruction of justice and conspiracy to obstruct justice, Kenneth Polite, U.S. Attorney for the Eastern District of Louisiana, said at a new conference.

They were sentenced to prison terms ranging from seven to 12 years, a significant reduction from the initial terms which would have kept them incarcerated for decades.

A fifth former officer, Arthur Kaufman, who was involved in covering up the crimes, was sentenced to three years in prison after pleading guilty to conspiracy to obstruct justice and a related count concerning fabricating evidence, Polite said.

"While this is certainly an imperfect resolution, today's proceeding ensures that these five defendants will be held accountable for their criminal actions," Polite said.

The former officers were credited for time already served, according to the Times-Picayune/ The four involved in the shooting have been in prison for nearly six years, the local news outlet reported.