Before the Ghostbusters had arrived on the scene, Fernando and Jonathan had a confrontation with a ghost. Jonathan's scream apparently had scared off the flying ectoplasmic entity. Jon had them look around the place for the ghost.
Later, in the main theater the Ghostbusters started firing at the ghost, for which Jon was worried they'd hit the art deco designs in the room. As a piece flew, he screamed.When the Ghostbusters had caught the ghost, Jon walked out with them.