Yes, but it's important to not immediately assume that it's because they've been killed.
I'd wager a statistically significant amount of whistleblowers are actually just liars looking to get recognition. When their lie catches up with them, they realize they've lost the one thing they had going for them and decide to end it all.
In the digital age where information can be shared so freely and so easily, there's not really an excuse for whistleblowers to be like "wait until THIS date" before revealing their information.