Jim Geraghty of National Review and Greg Corombos of Radio America are horrified to see another high school shooting, this time in Maryland, but they are gratified to see the school resource officer intervened quickly to neutralize the shooter.  They also react to the news of a driverless vehicle killing a pedestrian in Arizona and explain why humans behind the wheel will always make more sense than a computer.  And they pop the popcorn as "Sex and the City" actress Cynthia Nixon mounts a liberal primary challenge to New York Gov. Andrew Cuomo.