Adam Lanza, a 20-year-old recluse from Connecticut, brought terror to Newtown's Sandy Hook Elementary School on Dec. 14, 2012. The troubled young man, armed with a semi-automatic rifle and a handgun, entered the school and fired 154 shots in a span of about five minutes. In the aftermath, 20 first-graders and six educators were left dead. Lanza then took his own life. It was not until later that day that authorities discovered an additional casualty — Lanza's mother, Nancy. He had killed her in their Newtown home prior to the school shooting.