Once u get to the second floor, jump on the boxes, break da grate, and enter the ventalation, after that go to until u see the electrical thingie, press CTRL twice, aim it at hook on the top, and click. Go down as low to the lightning as possible, and when it stops hold right click, once u see a soldier, stop going down, take out ure gun, and shoot him in da head with a single shot, press the use key to jump off.