The body count will be high by the time this train gets moving.
We can interact with the locker on the left without being shot, so getting it open is a good idea.
Look for someone that might know the guards' secrets.
They probably wouldn't be very popular.
Visit the detention cells, and move to the far right.
Exhaust dialogue with the prisoner who tells us:
Remember the password-locked locker in the geology lab?
Assuming you exhausted dialogue options with the prisoner, you can 'grab' the locker to input the password.
The scarf belongs to the nearby guard, so show it to Ralf and enjoy the show.
The room is clear - jump back over to these hints!