Alex had killed the two mercenaries guarding the area near the control center. Of course, he fooled them into going into an area that wasn't under surveillance. Alex killed the first one by breaking his neck, the latter one he killed using his knife by quickly piercing his throat. Alex took the outfit of the merc that wasn't bloodstained, and as he predicted he had an ID card.
Alex needed to move fast, because once he went out of this room, and the people who were watching from the control room noticed he was alone then it would be game over for him, and the hostages.
From this room to the control room, if Alex walks it would take around ten seconds to reach, two seconds to swipe the card, and another two to kill the enemies in the control room. So overall fourteen seconds to move.
After he was done wearing the mask and outfit of the fallen merc, Alex took the dead merc's weapon. Alex breathed slowly as he left the room.