i have notice there be a couple of poster or viewer who believe that pierce be the one who strangle clean willy and although we do see sean connery character be see by willy and that why he run and we do not ever see pierce actually chase willy a he run through the city street . i believe it be one of the old henchman in pierce gang who kill willy . if you stop the frame where the killer be stand outside the building after do the deed you can clearly see the man be definitely old and short than sean connery be and he be not dress as well and he also be not carry the cane that connery be hold earlier in the tavern scene . it be more likely that pierce be the unseen person distract willy with the object fall down the stair . check it out . great book . good movie .