To complete Aztec, you normally need to beat Jaws, get the key card he drops, and head back across the level so that you can get into the locked room. To open this locked door without beating Jaws, simply stand at the glass door and shoot it to attract attention. When you see the door next to you start to open, run and hide behind one of the shelfs in the room. One of the guards should go to where you were standing, and open the door to go looking for you. Charge at him and get into the locked door before it closes.