Killing a whistleblower is never a good idea. Look at how much bad press Boeing is getting right now, the only reason why I knew about the Boeing failures is precisely because the Boeing whistleblower "mysteriously died."

If Grusch, et al. mysteriously dies then you know your answer. But the powers that be will never do that, because that would legitimize the whistleblower's claims to some extent.

That said, there have been sort-of high profile mysterious disapperances of people linked to UFO conspiracies in the past.