1) First run out and turn right then left after you pass the one guard. Don't shoot him. After you turn left zig zag so the people behind you don't shoot you. When you get to the gate open it and run to the next opening across from you and run through. Turn left and run over to where the safe key is. Open the door and stay to the right. Snipe in and shoot the guy on your left. The guy on the right will run out and try to kill you, so you kill him. Then go in and turn right. Inch around the crate until you see a few guys shoot them and beware of anyone who might come up from behind. Shoot the projection screen at the back of the room. Once no one is coming go to the left next to the door you came in.
2) Inch out until you can see the drone gun in the corner. Stay near the door and turn to you right but don't move. Aim at the drone gun and blow it away. This takes a few tries to master but it works.
3) Once the drone gun is gone run into the room and make sure no one is in there. Then pick up the key on the desk.
4) Turn around and shoot the two mainframes and then run out of the building. When you open the door there will be two or more guys there. Shoot them and then run out and turn left. Charge the guys that are croched down shooting at you. Shoot them but don't stop. Once your past them start to zig zag so they don't shoot you. Then run to where the safe is.
5) When you get to the warehouse that the safe is in open the door and run in. Go left and then right and you will see stairs. Run up the stairs and turn left and then left again. Go to the safe and open it (you don't have to select the key. Just open the safe like a door.).
6) Turn around and run for the door across from you. There maybe a guy there. Kill him and open the door. Run down the stairs and run over to the garage doors. Open the one closest to you. Run over to the train and jump in without killing the guys in the train.