Dr. Fred Schiller is an NYPD departmental forensic psychologist who specializes in profiling terrorists. In the film he evaulates Simon Gruber and his grudge against John McClane.
Die Hard with a Vengeance[]
Dr. Schiller sees that Simon is a textbook megalomaniac and that he wants control over McClane. He says Simon wants to pound on McClane until he kills him. He also determines that the name Simon is probably not an alias and it's actually his real name with some variation. When Simon calls in, Schiller listens in on the call. After the call, Dr. Schiller finds that Simon spoke German, called it his Fort Knox and stammered when McClane pushed him during the conversation. He also says that Simon cannot be brought, which lets McClane, Inspector Walter Cobb and others know who they are dealing with.