A tragic mass shooting at a Florida high school leaves 17 people dead. As the nation mourns, the debate over gun control and mental illness is reignited. New indictments in the Russia probe, as various Russian nationals and entities are officially charged with meddling in the 2016 election. Plus -- fallout from former White House aide Rob Porter's resignation continues. CBS News Correspondent Steve Dorsey will have these stories and more on the CBS News Weekend Roundup.