Ever since he was a kid, Mark Schultz idolized his older brother. So when Dave Schultz was murdered in cold blood by his athletic sponsor, the eccentric millionaire John du Pont, Mark's entire world was turned upside down. "Losing Dave was like losing my anchor," Mark tells PEOPLE. "Dave was like a one-man cult and I was his follower. When he was killed, I was left floating free, wondering what to do." Mark recounts the story of his brother's senseless death in his new memoir Foxcatcher, out Nov. 18. The events are also the basis for a movie of the...