It's already been released. When he is talking about a key, he means an encryption key. The files probably have dozens to hundreds of copies with many different people, it might even be available online. And several
people he trusts have the key to decrypt the files.
Releasing it would be the only insurance. There is only one revelation that would rally the people to your defense and protect you, this is it.
Keep it a secret and they will kill you and find your evidence.
It's already been released. When he is talking about a key, he means an encryption key. The files probably have dozens to hundreds of copies with many different people, it might even be available online. And several people he trusts have the key to decrypt the files.