Just the guys assigned to that server/site I imagine. From that movie "Safe House", it showed (presumably thanks to research or a military/intel advisor) that CIA outlets are mostly manned by small crews. While the teams with guns are dispatched only when there's an alert from someone with the proper emergency codes. If they hit it fast and got the minimal guards and ranking officer, then no alert goes out to the back up teams until whatever regular check-in time comes and goes. Lightning strike. I think in general the CIA runs itself similar to terrorist cells. Small units and operators using very specific communication practices. Drawing their budgets from non-trackable sources. No big central target "bad guy lair" full of cannon-fodder just hanging around to be lit up in big crazy action set-pieces. Also, one of the Black Hats on site may have been an undercover/turned White Hat Agent who simply opened the door for them, making the whole thing super-clean.