Some of America's Deadliest School Shootings

Two 15-year-old students shot to death at Marshall County High School in Kentucky are the latest victims in a long line of shootings that have played out at schools across the country. One of the earliest incidents took place in 1966 at the University of Texas in Austin, where a gunman positioned himself on the observation deck of the UT Tower and took aim at people below.'s Mara Montalbano ( has more.