In Frank Sheeran's book he makes a dubious claim that Marcello used to fly zips in to commit contract murders. Then they would be chauffered back to the airport and then the zips would be murdered too. I also read (sorry don't have a source right now) that Marcello used to direct strangle lieutenants he believed were skimming and then bury them in the swamp.

Interestingly, that does not provide any names of victims.