Lil Wayne -- Major Beef in the Club Before Tour Bus Shooting

The search for suspects in the Lil Wayne tour bus shooting might lead back to the Atlanta nightclub where he performed that night ... and a heated showdown he had with audience members.

Sources in Compound Nightclub this weekend say Weezy got into it with several people in the crowd. It's unclear what was said to spark the dispute, but we're told Wayne was hot as fish grease during part of his performance.

We're told club security eventually booted the hecklers, but just to be safe ... Wayne got extra protection while leaving the club and getting onto his tour bus.

As we reported .. the shooting went down minutes after the bus left the club.

Police have no suspects yet -- and continue to investigate -- but the near-melee could be a clue.