By a barricade, I assumed you meant it would be locked.......If it wasn't he just opened it up and walked in.
You walk in... right into the Guard barracks. By a quick look-around there are roughly 10 people scattered among the bunks and the grouping of tables towards the center of the room. Somehow, nobody spotted you.
You come to a well-lit corridor; on each side of the corridor is one door, both even with each other, and straight down the corridor you can see more stairs.
The door on the left opens with the keys, and behind it is a metal grate with a grate door in the middle. Behind it, what seems to be an Armory. Sadly there is a chain and pretty big lock keeping the door shut.
The door on the right doesn't open to any of the keys.