Weapon used in San Francisco killing belonged to federal agent
CBS News has learned the gun used by accused gunman Juan Francisco Lopez, an undocumented immigrant with multiple felony convictions, belonged to a federal agent. He pleaded not guilty Tuesday and has been at the center of a debate over San Francisco's "sanctuary" policy, whereby local law enforcement is prohibited to cooperate with federal immigration authorities. But the policy debate is being eclipsed by the unexpected twist in the crime itself. John Blackstone reports.