GoT Se4 spoilers

"Also happening in Game of Thrones Season 4 is the death of Tywin Lannister (Charles Dance). Tyrion Lannister (Peter Dinklage) kills Tywin after learning of some maddening revelations from his brother Jamie (Nikolaj Coster-Waldau)."
http://au.ibtimes.com/articles/554084/20140529/game-oh-thrones-season-4-episode-8.htm#.U4bOySBOLIU
In the books: After murdering Shae, Tyrion finds his father on the chamberpot. The two engage in a rather tense conversation, and Tyrion ends it by shooting his father in the stomach with a crossbow. The elder Lannister bleeds out on the toilet