Who killed JF Kennedy?

[Master]

I watched a "recent" documentary and they suggest that Oswald did fire the bullets but the fatal shot was done by accident from one of the bodyguards behind the president. They wanted to hide that fact due to embarassment and hid the brain and covered the whole thing up.

Well, the shot couldn't have come from Oswald's cheap rifle, because it couldn't fire exploding bullets.

http://www.garyrevel.com/News/press_release_11.html

But was it an accident?

I know it seems highly unlikely but at the same time it could explain why they would want to cover it up.