I have just given the saw to whoever it was behind the door in the computer room...
Spoiler below!
...and suddenly I find myself locked in the room with that... thing chasing me. Got the 3 cards but now I can't seem to be able to get out (or kill the thing either). Accessing the computer gives me a "no time for this" message, and I can't find anything interactive on or around the electric boxes.
get him to follow you to the room which can be closed (looked like a fridge or something not far from the big computer with 3 cards) and close the door... he will not be able to get out (if you understood which room i mean)