After you enter the building you go down a flight of stairs and get a CS in which you do a bit of bragging and then you jump across a gap in the stairs. Head down to the next level and you'll see a soda machine that somehow still has power - nice cold drink budeee!
Down the hall is a door, and when you kick it open an enemy tries to grab you as a meat shield but your partner takes him out with a clean head-shot and you are back in business. Through this room is a drop-down and another pair of soda machines - and some more bodies. At the end of this room you spot two PMC's about to execute some more hostages across the large gap in the buildings.
This is where you get the tagging tut, so go ahead and use GPS and tag the guy on the right, then use your sniper rifle to take-out the guy on the left. Nicely done! There is a boost-point next to you but after your partner boosts you up the floor collapses beneath him! You are going to have to hook up later it seems...
Fight through the cubical farm and pass another soda machine and head down the ramp here, loop around and take-out the bad guys, and then down another ramp and another group of bad guys. Down the next ramp you confront a mounted gun and some shield toting merc's - go to the desks to the right and lob a grenade in to take out all of them in one go!
As you move past the mounted gun you reach a gap where you push down a section of wall to make a bridge - as you cross make a sharp left turn and head through the hole in the wall as your partner joins you.
Collect the Fifth Radio
Just inside here is another boost point, and once you are both up, head into the room on the left and take out the bad guys, and collect another Radio (Radio 5 of 14) sitting on the desk here. There is a supply crate here and you get an update on Alice.