The FBI acknowledges it failed to tracked down school shooter Nikolas Cruz after being tipped off to a threatening YouTube post, but that missed opportunity was not the only red flag missed. Nancy Grace discusses the investigation into the massacre at Marjory Stoneman Douglas High School with experts, including hate crime expert Brian Levin, security analyst Rob Hessell, former DEA agent David Katz, forensics expert Joseph Scott Morgan, child welfare law specialist Ashley Willcott, psychologist Caryn Stark, and reporter John Lemley.