help help help i am 100% stuck i have to get a key code but it wont give me it how do u do this please help

I'm stuck on this too. I used the remote modem on the computer. then marshall starts talking. the timer starts and i run up to the keypad but don't have a passcode. ive tried doing the remote modem on the compo again but i run out of time. do you have to kill all the guards first? maybe you search one of them and find the code... i havent tried that. i snuck around the room and only killed the one guard nearest the door... im not sure. i keep running out of time. if you figure something out, tell me