Yes it is the person. Get yourself a bazooka, a grenade and a gun. Place them all on the very same table. Now wait, see what they do, document, record video. My hypothesis; You will find that nothing happens. Now show them to a person who wishes to harm other people and see what happens. My hypothesis is dead people. I'm a good guess you'll find, that's that common sense people carry on about.
So bazookas and grenades would be more effective? Why is that? I would guess people would have a tough time lobbing grenades accurately. Is a bazoka a better aim? Wouldn't people just leave that heavy gear at home, get lazy? Wait lemme guess, no common sense went into this idea of yours?
Make sure there are no mirrors in the room when you cry, "common sense gun laws". If you haven't guessed yet my theme here was the lack of any sense, common or not.