It all started with an uncertain smile and a nervous laugh at a press conference a grieving young father didn’t even know he was going to be holding. On Friday, Dec. 14, 2012, Robbie Parker’s world imploded when his 6-year-old daughter, Emilie, was among 20 first graders and 6 educators who were killed in one of the worst mass shootings in U.S. history at Sandy Hook Elementary School in Newtown, Conn. Inundated with calls from reporters, Parker, a neonatal intensive care unit physician’s...