Documentary explores Waltham slayings' ties to marathon bombing

A new three-part documentary from ABC News Studios, "The Murders Before the Marathon," focuses on Boston marathon bomber Tamerlan Tsarnaev's ties to a 2011 triple homicide in Waltham. We talk to independent journalist and documentary producer Susan Zalkind, a friend of one of the homicide victims. We also hear from former Boston police officer Tom Nolan.