NBC Nightly News Full Episode - Dec. 13

Tonight, breaking news. The active shooter incident at Brown University. School officials alerting students to lock their doors, silence their phones, and take cover.The late developments just in. Also breaking, the deadly attack on American troops in the Middle East. Two Army soldiers and a civilian interpreter killed in an attack in Syria, according to the Pentagon, in what officials say was likely an ISIS ambush.Tonight, President Trump's warning the US will retaliate. Tens of millions on alert for snow ...