Okay, maybe not the best example since the Warren Commission was in charge of the coverup. Which, by they way, is important to remember when people rush to say the Secret Service, CIA, or FBI would NEVER try to take out a President.
It is also important to remember that the CIA boss was a JFK appointee (McCone) and he was totally out of the loop.
It was a former CIA Director (Dulles) who was neck deep in the plot and the coverup.
Btw LBJ later fired McCone over a policy difference.
I leave as an exercise what that policy difference was—and how it related to the JFK assassination.
:-)