I read a manga awhile ago that was similar to Battle Royale, and after hours of searching by myself, I can't find the name.

Synopsis: A bunch of adults get trapped on a location. Supposedly, there are no laws, so these people can do and behave however they like. The people come from different backgrounds: some are criminals, some are regular civilians, like teachers.

I specifically remember in the first few chapters, it focused on a large, brutish criminal who was bullying people.

Can somebody help me identify the manga?

Was it EX - Shounen Hyouryuu?