You know what happened to Presidents Lincoln, Kennedy and Reagan. Now, look at a series of 10 shocking secrets behind assassination attempts you haven't heard of. Before Lee Harvey Oswald, a 73-year-old postal worker schemed to take the life of then President-Elect John F. Kennedy. When President William McKinley was shot in 1901, his surgeon didn't scan the wound with an X-ray. The secret: If he had benefited from the aid of modern-day technology, doctors might have saved his life. (Source: National Geographic Channel)