America's Book of Secrets S04 E02 Protecting the President

The United States has experienced four presidential assassinations, and two more assassination attempts nearly succeeded. But how many more occur that never reach the public? And how far do we go to protect the commander in chief?The United States has experienced four presidential assassinations, and two more assassination attempts nearly succeeded. But how many more occur that never reach the public? And how far do we go to protect the commander in chief?