On the morning of December 14, 2012, authorities say 20-year-old Adam Lanza walked into Sandy Hook Elementary School in Connecticut and opened fire, killing at least 20 children and six adults before taking his own life. Investigators believe Lanza shot and killed his mother at a nearby home before the massacre. Who was Adam Lanza, and why would he carry out such a senseless act? Dr. Phil goes behind the headlines in this tragedy in search of answers. Plus, would you know if you were raising a killer? In a very rare and emotional interview, hear from Jeff, whose son, Andy, became a school shooter. He says in 2001, his then 15-year-old son went to school with a .22 caliber revolver and 40 bullets in his backpack and opened fire on his classmates. Jeff recounts the tragic day and shares the signs he says he may have missed in his son. Plus, hear Jeff’s tearful warning for all parents.