After 26 victims were killed at Sandy Hook Elementary in Newtown, Connecticut, it was called "an unprecedented opportunity" for gun control. Grieving parents vowed to fight for what they called "sensible solutions to prevent gun violence." Even some politicians with top ratings from the NRA suggested they'd be willing to consider new gun control measures. One year later, it hasn't turned out that way. That's according to a report by the PBS series Frontline, where Sarah Childress is an investigative reporter.