How to take a hostage?

[imbitable]

Hi,
I'm in mission 6 right now and I have the feeling that I'll need the guy sitting on the toilets on the right to enter "safely" the main room. But I don't get it: how do you take a hostage with the Xbox 360 controller? In the options it says to use "A" but i frag the guy all the time. I'm sure that it's a very easy thing...
Thank you for your help.

[Rob Lowes Dream Sequence]

Pretty sure you can only take a hostage if you have a gun in your hand. Melee weapons wont work.

[Mr. Hans]

Correct, you need a one-handed gun (so you can grab the guy with the other hand).

[imbitable]

Thank you guys. I will try that.