That said, I think people need to recognize that in many aspects what's happening is connected to societal issues that gun control and gun regulations will have very little impact on - remember, even in Japan somebody could make some kind of battery ignited home-made shotgun and kill Shinzo Abe.
Countries with strict gun control enjoy far lower rates of firearm accidents, suicides, and murders. IMO it's clearly worth the tradeoff. Very few of us live in a place where only guns can solve our problems.
The fact that occasionally someone goes to great lengths to kill doesn't mean we should make it easier for everyone.
In which case you'd need a strong internal investigatory services in order to root these plots out before they happen by following up on leads and tips.
Well... not to get political, but I think we're hollowing that out too?