As far as I've thought about it, I've always thought of Mark Halperin too. He's one of the few I can think of who actually makes witticisms (about both killings). When his friend Hugh is worried about what he'll do to the blackmailer, Mark says very innocently, "Why, Hugh - I'm no more violent that you are." And of course when Hugh, referring to his (partly accidental) killing, says, "I knew I should have called the police," Mark says, "You DID call the police." Two pretty great lines.