Well, there's enough direct evidence to show that Lee Harvey Oswald was in the book depository with a rifle shooting at the President, but whether or not he was the only one or who put him up to it is unclear. I'm kind of at a point in my life where I think it's pretty likely he really did act alone, as it appears to me that all the varying events leading up to and following the assassination seem to be too disorderly to be truly planned out, but I think that if he didn't act alone, he was likely influenced by someone connected to the US Govt in some fashion.