Proof that checkpoints leading to gun free zones just move the target rich environment from inside the sterile area to the queue outside the checkpoint. I would also point out that New York's laws against guns, as well as Federal regulations against carrying firearms in Federal buildings and post offices failed to work. Again.
How many times do gun free zones have to fail before people realize that they do not work?
There are those who will claim that the armed guard had a gun, and that did not work either. I would answer with this: Simply standing around with a gun is no guarantee that you won't be ambushed and killed. You need to be willing, able, and prepared to use that firearm, or all it means is that you will carry around a hunk of metal that is used only for decoration.