Classic blaxploitation movie starring Fred Williamson
Black Caesar
(1973)

Tommy Gibbs (Fred Williamson) grows up to be the leader of a black maffia outfit in Harlem. He gets so big that he takes over the Italians turf as well but his world falls apart on him.  He ends up shot and stumbles across town to his old decayed neighborhood whereupon he is attacked by a group of teenage thugs who rob and beat him to death not knowing who he is.

Thanks Ed!