When the mission begins, make your squad rappel down the left part of the 
building. Then, order them to go down until they are able to breach. Next,
go to the middle of the roof with the opening. Drop a C4, incendiary, smoke,
or frag grenade, and keep shooting through the glass. After a few seconds, 
order your squad to breach into the building. Finally, rappel down into 
the building.