Spring the news far and wide first. At the same time, announce you have no medical or mental issues and that you suspect individuals want you to meet an untimely death. Then let the chips fall where they may.
Once you “spring the news” you are no longer a valuable target and things could get complicated if your adversary offs you. Then because there is always a chance of the job going awry and coming back on the assassin. Once the news is out there is no reason to kill the bearer. Prevention is high value. Revenge is not. If Breitbart had kept his mouth shut until he made his revelations we would surely know a lot more about things than we finally learned.