Romeo ultimately kills Tybalt in Act 3, Scene 1, of "The Tragedy of Romeo and Juliet" because Tybalt kills Mercutio, Romeo's close friend. Initially, Romeo refuses to fight Tybalt, who is now his kinsman by marriage to Juliet, and tries to maintain peace. However, when Romeo tries to intervene in a fight between Mercutio and Tybalt, Tybalt fatally wounds Mercutio. Overcome with rage and grief over Mercutio's death, Romeo kills Tybalt to avenge his friend's death. This act of vengeance triggers Romeo's exile from Verona and marks a turning point in the play's tragic events.