When will the first murder occur with a printed gun?
When will the first accidental shooting occur with a printed gun?
When will the first child be killed with a printed gun?
When will the first suicide occur with a printed gun?
When will the first robbery occur with a printed gun?
When will the first car jacking occur with a printed gun?
When will the first plane hijack attempt occur with a printed gun?
These are the real world events that no-one in the pro-gun world is willing to acknowledge. It's not a case of if these will happen, but when.
Guns don't make the person carrying one any safer. Remember Christopher Dorner, the rogue cop in LA? He killed two police officers and wounded three others. These were armed trained professionals and they were knew ahead of time that they were the targets. They weren't stupid, they followed protocol, and they all got shot.
Even if you have a gun, if someone gets the drop on you then you are at their mercy. If you think otherwise you're stupid. Rambo, Chuck Norris, John Wayne, James Bond, etc. are people in movies. That's not the real world. Your chances of pulling out your gun and saving the day are something like your chance of being hit by lighting. Saying that you need guns to be safe is a mark of mental instability. As long as you are within shooting range of a gun you are less safe then you would be otherwise. It's simple physics.
I think the first person to be wounded by a printed gun will be in an accidental shooting. This will happen relatively often, because a lot of untrained people will decide to do this with new cheap 3D printers. I also expect there will be a disproportionate number of shootings involving children, because printed guns will seem like toy guns to them, or they will make a mistake. But hey, as long as you have your little penis substitute to make you feel all manly and tough, why should you care?