Small nit to pick: South Korea, Taiwan, and Argentina had rather nasty governments up until 1990 or so. Read about the dirty war in Argentina or military law and the banditry laws in Taiwan.
I’m not sure if registration or wait period would have helped prevent what that guy did. He bought his guns legally, and long before the crime. Wait periods only help deter people who act rashly. Registration doesn’t matter, since the guy never intended to avoid being “caught” and the police saw no cause to take action against him before the crime.
