Mr. Sullivan is a character in Clock Tower. He is the curator of the Municipal Library. An extremely intelligent man, he appears to have a longstanding work with the University Research Building, and is one of the two candidates for Professor Barton to analyze the Demon Idol.
If the player decides to give the statue to Mr. Sullivan in the Prologue and, later on, have Helen Maxwell go to the library, enacting Scenario 2, upon asking Mr. Sullivan about the statue, he would ask Helen to come back to his office later to pick it up.
Later on, when the old clock tower of the library mysteriously tolled, Mr. Sullivan and an accompanying Helen went up into the clock tower to investigate. Believing that someone messed it up, he peers out of the peekhole to investigate, only for the minute hand to come down and decapitate him. Shortly afterwards, Scissorman jumped into view from behind the clock gears, implying that this was not an accident.
If the player decides to give the statue to Rick in the Prologue and, later on, have either Stan Gotts (Helen's Scenario) or Nolan Campbell (Jennifer's Scenario) go to Rick's house, enacting Scenario 2, Mr. Sullivan won't be involved in the case; thus survived.