In the past month, 57 Americans have lost their lives to gun violence in eight incidents, which included mass killings of 10 and 13 at a time. The shooting victims included children and other family members, nursing home residents, immigrants and police officers. In recent months, a church, college and day center all have been shot up. It appears the shooters all acquired their weapons legally. Gun control advocates have renewed calls for action, but as one political scientist put it, “the silence has been deafening” -- from the state legislatures, Capitol Hill and the Obama White House. We explore that issue and hear from a US agent who tracks illegal firearms that move from the US to Mexican gun cartels.