The New Orleans PD says a fully loaded 9mm handgun was recovered from Will Smith's car after he was fatally shot.
Cops made the announcement Tuesday afternoon -- after finally executing a search warrant that allowed them to search Smith's Mercedes.
The discovery will undoubtedly help the defense -- which is claiming Cardell Hayes felt threatened by Smith at the time of the shooting.
At least one witness has claimed Smith said he was going to get his gun during the heated argument following their fender bender ... and that's when Hayes pulled out his weapon and opened fire.
Cops say they're still investigating and interviewing witnesses -- including Smith's wife and the 2 additional passengers in Smith's car.