After receiving the Black Arrow from his son Bain , Bard constructs an improvised ballista .
After receiving the Black Arrow from his son Bain , Bard fires the Black Arrow at Smaug 's weak spot , which successfully hits its mark and kills Smaug .
After receiving the Black Arrow from his son Bain , Bard constructs an improvised ballista and fires the Black Arrow at Smaug 's weak spot , which successfully hits its mark and kills Smaug .