OMG, pls. let us know how Benny is doing after all those bites…
If I were you, I would still report the incident to the police or Animal Control... It doesn't matter if you don't know who the owner is...This would establish history and should the owner be identified, then there's documentation that the proper authorities can look back to...
Also, you said you've seen this pit bull before... If you see that dog again, maybe you can observe it (from a safe distance, of course) and maybe he'll lead you to its home... But safety (your safety) is priority one... Just my $0.02...