OK, so I'm playing this game free online on that Core Online thing that Square Enix is doing. I've started myself on Expert because I like to challenge myself (but not too much). I got to the part in the first mission where you stow your gun in the crate full of baking soda and have to walk into the control room with a guard standing in front of the doors. Every time I walk past him with the crate and the chemist's suit on, he notices me and starts following me (yellow alert meter). When I try to open the door to the control room, he starts shooting.
What am I doing wrong? I'm doing what the game told me to, or so I think.
Thanks for any help in advance.