After killing the first four men, turn right, go through doorway, and open the barred door. You will hear someone say "Hey, what's going on?" To your right is an open door with two men in it. One is armed with a S/W 10 and the other has a pump shotgun. After you kill them, look on the floor near the file cabinet. You will find a crowbar. Equip the crowbar and press ACTION. You will see a cinematic featuring Tommy prying the lock off. There is also a door to a balcony that is very easy to shoot the dogs from.