Rachel Maddow Takes Us Through 50 Years Of Mass Shootings. The Trend She Uncovers Is Devastating.

The shooting in Navy Yard, Washington D.C., on Sept. 17 that took the lives of 12 and injured eight others was both tragic and terrifying. Unfortunately, mass shootings like this one have also become an all-to-familiar way of American life. Watch Rachel Maddow explain why it hasn’t always been that way and uncover an alarming trend at 5:20.