The people breaking down doors and taking firearms from law abiding citizens were almost exclusively out of state law enforcement and Oklahoma National Guardsmen, at least on film. Ordering or at least publically advocating the confiscations were Mayor Ray Nagin, ex-Police Chief Eddie Compass, present Police Chief Warren Riley (who has stated he will give a repeat performance this hurricane season!) and St. Tammany Parish Sheriff Jack Strain. The confiscations occured not only in New Orleans, but also throughout Orleans Parish and St. Tammany Parish. I seriously doubt if anyone is now going to step forward and say they were the "hands on" participants, unless they were captured on film.
To answer your question, it appears that no record of firearms sales was used to locate citizens with guns. Homes were broken into, and if residents were found, they were compelled to evacuate. They were asked if they had firearms. If the citizens said yes, the firearms were taken at gunpoint. This occured in their homes, in boats while attempting to evacuate, and along roadways at checkpoints.
Strangely, when Duck Season opened in St. Bernard and Plaquemines parishes hunters were allowed through checkpoints with their shotguns.
