Most obvious person to report it was the head of security at Los Alamos; Feynman told them about his exploits and actively tested the security.
It's only logical that it is this way, but it's also very sad that learning more and adapting your world view to your growth is orthogonally opposite requirements for intelligence work. It also shifts an incredible amount of weight on who leads all the blindly trusting agents of state.
The FBI can be over the top, but I imagine that's probably worth having a conversation about.
Edit: the letter (from Bell?) starts on page 110 of the file... It's pretty extreme!
[1] https://en.wikipedia.org/wiki/Klaus_Fuchs
[2] https://en.wikipedia.org/wiki/Klaus_Fuchs#Value_of_Fuchs.27s...
She made him sound like a James Bond evil genius type:
In matters of intrigue Richard Feynman is, I believe immensely clever—indeed a genius—and he is, I further believe, completely ruthless, unhampered by morals, ethics, or religion—and will stop at absolutely nothing to achieve his ends.
[1] https://robertlovespi.net/2014/09/07/how-richard-feynman-sav...
https://en.wikipedia.org/wiki/Manhattan_Project#/media/File:...
Gladys Owens, the woman seated in the foreground, did not know what she had been involved with until seeing this photo in a public tour of the facility fifty years later.