We can make the message vague enough so that it won't point fingers directly at us, but it'll still give out information. Like... "One down, two to go," or something along those lines? If the Prophets do suspect us, that will basically confirm that we exist for them. But the others may not piece that bit together.

[ which is fine. as long as they give some sort of hint about the prophets' existence, and that there may be another way to solve this without murdering everyone until there's only three left. ]