Now go through the door into a large room which has blast doors on the left. As you turn right at the end of it you’ll see 3 boxes against a door, but before you move the boxes to go open that door grab the ammo in the room to the right.
The way forward is down a corridoor on the left. Headcrabs can easily be stabbed if you strafe as they jump, then stab them as they land. You can get away with knifing some zombies if your ammunition is too low. You should get a submachine gun from going under it.
Move forward keeping right as you kill a few zombies and then crouch under the broken door using (left control). Make sure to get the knife from the dead Black Ops agent.