I've done similar things to players. We had a GURPS game using the WOD books they had put out at the time. Some of the players were worried about the Garou that was stalking them but I actually heard 2 of them tell the rest not to worry I'd never do anything that would let a player die... So, sad. It WAS a horror game after all. So, they were have watches during the night and one of the players decided to do it solo sitting in a car... He never knew what hit him. By the time the surprise was over he was being torn to pieces by the werewolf. :)
The shocked silence in the room for the next 5 minutes was awesome and for some strange reason they got a lot more cautious after that... go figure.