For the record: I actually know that this CERN human sacrifice video thing is, indeed, a fake. But if it wasn’t a fake, this is the way to do what the Esoterrorists RPG calls a veil-out:
— Uncaring Cosmos (@UncaringCosmos) August 18, 2016
Come up with a plausible mundane explanation of the video, establish that it’s an internal disciplinary matter instead of an external one, and most importantly, don’t make a big deal about it. If you’re covering up an actual successful ritual human sacrifice at a symbolically-powerful place on a symbolically-important site, this would be the way to do it. People running horror games, take note. People playing in horror games, likewise.