Hagwon English instructor turned out to be gangster

Another ‘gangster’ posing as an English teacher has been arrested in Seoul.  A previous incident of Korean-American ‘gangsters’ is what prompted the review of F-4 applicants for teaching positions.  Foreigners (including myself) argue that these incidents only represent a very small fraction of the overall foreigner community (especially English instructors) but I wonder why new hurdles they will come up with now.

I read somewhere else that the most recent suspect did not even have a high school diploma.  Therefore, the problem is not only the suspect but the schools that hired him:

After committing the crime, he escaped to Korea and worked as an English instructor in private institutes in Cheongdam-dong and Mok-dong.

Why aren’t they checking these things?  It seems that they think that anyone with an F-4 who speaks English can legally teach.  Articles in Korean did imply that this person was legally residing in Korea so I can only assume that he had an F-4 visa.