Similar sorts of things have happened in the Great White North. In 1989, Gamil Gharbi (aka Marc Lepine) was given a Firearms Acquisition Certificate by a Montreal police department firearms officer who failed to do the proper background check on Gharbi, which likely would have revealed that he had been turned down by the Canadian Forces due to mental instability. As a result, he was able to legally purchase the Ruger Mini 14 sporting rifle he used in the December 1989 rampage at Ecole Polytechnique. But FACs, when introduced in 1979 for standard hunting rifles and shotgun purchases, were supposed to have kept such people from legally buying guns.
PS: And this is by political design!