the nopd reverts back to what it knows.everts back to what's comfortable, what's convenient, and to what the existing culture has always been. >> almost immediately, you saw, discipline stopped, accountability stopped. by the time we came to katrina, this department was, i would say, in as bad a shape as we had been in 1994. and that storm stripped bare any pretense that there was any structure, any accountability, any of the... the skeleton that you would expect of an organization like a police department. it all vanished. "the courts are gone, the jails are gone. it's up to us. and we're going to, 'do what we have to do and move on'." >> narrator: according to officers who have pled guilty in the danziger bridge case, a cover-up of the killings began almost immediately. >> a lieutenant told the officers involved in the shooting to get their stories straight. there were secret meetings held. one man is accused of getting a gun from his house and filing it into the court record as being a gun that was used by civilians on t

and i would have to say that it's not katrina that caused nopd to be like it was. it just manifested the dysfunction. >> reporter: still, most of the city's residents came back after katrina. it is believed about 75% of its close to half million former residents have returned. but the struggle to rebuild has been monumental and, for some, coming home was never an option. >> lower ninth feels so much the same today, five years later, as it did a month later, a year later. the debris has mostly gone, but it is not a place where you feel a vibrant sense of return. >> reporter: every visit i make back here, i'm always stunned to see water marks still and roofs missing. that must drive you crazy. >> it does. those of us that have been here know that it is a very, very long process to rebuild a very intricate network and fabric of our lives. >> reporter: dr. irwin redlander of columbia university has been following a thousand families affected by katrina. >> we are seeing for the most vulnerable children down there, many are still not living in stable communities, in saf