Indeed Horatio !
We now have the farce that the flight deck door is ( apparently ) locked - but only until the crew are brought their meals, and / or regular drinks, and / or they want to use the loo, i.e it's actually unlocked & opened loads of times during most flights.
To say nothing of the fact that whilst the flight deck door might indeed be armoured to the extent that it can withstand a ballistic assault, i.e. that it can resist bullets being blindly shot through it, the areas outside of the frame which hold the said same door are not armoured at all !!
....... so, wanna pop one in the skipper on a B7737 ? It's easy, just go in the forward bog, take yer gun, aim it forwards ( i.e. through the mirror ) and blaze away - and similarly so through the RHS forward galley area to pop some in the FO.
But perhaps the best bit is that, because the flightdeck door is now so robust and ( once locked ) can only be opened from within the cockpit, should any of the above happen there is supposedly no way that anybody could then gain access from the cabin into the cockpit to rescue the controls.
Thus, as the pilots lie dead or dying, what now the Sky Marshall(s) - yer terrorist martyr has done his / her work.
So, oh what a shame that more wasn't done to stop Johnny terrorist from getting onboard in the first place, as this 'last line of defence' just is not !