ZERO'S PROFILE

I love the game o far :) but I'm stuck :D After I gave sleeping potion to that guy I went to the water place (forgot how was it called) There are two swiches, and one is opening the doors and another is for the bridge, but when I open the bridge I can not swich the doors to open, I fire into that bomb but still... what I'm doing wrong? By the way, the game is GREAT!!!