I don't know as I have ever heard it in quite this form. I recall Jonah Goldberg writing years ago about the pointlessness of gun-free zones, pretending to reason like the criminal and thinking "Well gee, I was going to shoot up a lot of people in that church, but the sign outside says it's a 'Gun-Free Zone' so I guess I'm out of luck. Curses! Foiled again." I think that can be extended.
There is much discussion about the types of weapons that should not be available to disturbed people, and thus, not available to any of us, or only with great difficulty. If only...if only...because he had weapons that allowed him to fire so many rounds at once, or at a great distance, and if only he wasn't able to get those guns so easily, he wouldn't have been able to kill so many people. It looks compelling at first glance, because we are only looking at the moment of the crime. Well, sure. If the criminal or terrorist had planned to make a big splash and break the record for most victims, but had only shown up with a small handgun, he wouldn't have done so much damage.
But such crimes don't occur in a moment. Step back even 24 hours from the crime. If a person wants to create a big death splash to show what a bad dude he is, or how much he hates those girls who rejected him, or how much better his religion is than ours, but all he can get his hands on are a couple of sharpened butter knives, he's going to choose something else. He's going to blow up a building, or bomb a train, or drive a car into a crowd. His point is to make a splash. If he can't make a big enough splash with guns, he will go find something else.
This does not entirely invalidate the argument of trying to restrict access to certain classes of firearms, but it comes darn close. One would have to learn what terrorists' and disturbed people's second choice is and compare it to the death rate of the firearms in question when used in splashy, attention-getting sessions.
If their second choice is generally bombing, maybe we wouldn't be better off.