9. Post Office in Edmond, OK, August 1986
A white guy got mad and decided to take it out on his coworkers. Patrick Henry Sherrill shot and killed 14 co-workers and then took his own life inside the post office where he worked. He thought he was being treated unfairly at work. Up to that point, only one other guy in US history killed more people in a single day.
Pixabay/Public Domain
