Washington Post database tracks all U.S. school shootings since Columbine

The Washington Post has spent years compiling a database of all known U.S. school shootings since Columbine in 1999, and found that more than 311,000 children have been exposed to gun violence in school. John Woodrow Cox, one of the reporters who worked to gather that data and the author of "Children Under Fire: An American Crisis," joined Tanya Rivero to discuss the findings and why the federal government does not track school shootings.