I run like hell as guards pour in from all directions to search for me. I make my way back to the lockers and quickly hide inside an empty one. When the heat is finally off I return to the previous location and silence the guard before he can sound the alarm this time. I head left instead and up some more stairs to the next passage that is monitored by a video camera. I can disrupt the camera with a chaff grenade or simply hug the wall and pass safely beneath the range of the camera.
More stairs lead up to the next floor with more patrolling guards.
Taking a left at the top of the stairs leads me to the storage room with some ammo and an empty box I can play around with. It turns out this is a popular spot for the guards to sneak off for a quick nap. I decide to make this guard's nap last a little longer before I leave and head down the other passage. I eventually arrive at a suspicious looking section of hall that is lined with explosives triggered by invisible laser beams. I can reveal the beams by lighting up a smoke or putting a bullet in that fire extinguisher on the wall.