I am not sure I am comfortable with anyone giving someone else a gun whether you know the persons criminal background or not. I think that if you are going to give or sell a gun to anyone it is your responsibility to know if they can legally posses a gun. In this case it appears the guy knew of the other guys criminal background.
My preference is that any gun sales/transfers go through someone authorized to sell them.
giving someone else a gun whether you know the persons criminal background or not I did say: hid or disavowed his past and I meant it.
The few times I've actually sold a gun, I asked, and if they would not have produced an ID and let me copy information, the answer would have been "No Sale"...
OTOH I'm not about to join Sara Brady and her ilk in calling for the closing of the so-called "Gun Show Loophole" which is nothing more than the ability of me to sell you a gun without also telling the State.