There are certain defensive procedures in place for the flight deck. Also, there will be no mention of how many of the flight crew were armed. The captain did the correct thing.
As an aside, how come nobody is asking about the "pictures of Pakistan" that this woman had? No comments from the passengers, no mention of the content of the pictures from media. The woman lawyered up real quick.
How can you say the captain did the correct thing? He opened the cockpit door when there was a disturbance in the back of the plane. I'm sure they have defensive procedures but those are last resort measures. OK, fine, perhaps the copilot was armed and could shoot the first guy through the door before the second bad guy got him and the pilot and gained access to the flight controls. No, the captain wanted to exercise his "command perogative" and see for himself. In a real attack, that would make a fitting epitaph for the captain, "he wanted to see for himself" but a tragic one for the rest of the souls on board. That door needs to remain shut and locked. period. The gun is for final defense against the door being compromised by explosives or brute force.