For example, do you know why John Wilkes Booth shot President Lincoln? Do you know that he didn't act alone, that he had the support of others?
It seems to me that seemingly random acts, such as the assassination of Lincoln, and of others, like John F Kennedy, are anything but random. In fact they are calculated, planned, and well organized events.
Have a read of Killing Lincoln by Bill O'Reilly and see why that particular assassination was the one that shocked a nation and changed America forever.