Turi's right: the operative syllable is "capo."
Tony Soprano personally whacked several people other than Matthew. That would be unusual by real-life Mafia standards because part of a capo's or don's power is to order others to do so. I always had the impression that Tony did the hits himself (or at least some of them) to thwart Christopher, who was always dying (no pun intended) to whack someone to pave the road toward being "made." However, dons have often ordered people whacked for personal reasons. Paul Castellano ordered his own son-in-law killed because he abused Castellano's daughter. Vito Genovese had his wife's first husband killed so he could marry her. Al Capone personally killed someone who had slapped around Jake Gusik, his bosom buddy, mentor and business manager.