Grimrock

So I'm in the room where the faces are supposed to start shooting as soon as you enter in order to solve the iron door puzzle. Except when I enter they never start shooting. Is this a bug or am I just missing something completely obvious?

Thanks for the help!

This sounds like a stupid question, but are you entering on the side furthest from them (across the gap from where they are)?

went wandering around the map for a while finding other secrets and came back and it worked. Strange. Anyway, thanks for the help .